NSDate - 时间日期相关操作方法总结

变更记录

序号	录入时间	录入人	备注
1	2015-03-30	Alfred Jiang	-
2	2015-12-23	Alfred Jiang	-

方案名称

NSDate - 时间日期相关操作方法总结

关键字

NSDate \ 时间操作 \ 日期

需求场景

需要用到日期显示和时间操作等场景时

参考链接

GitHub - DateTools

详细内容

######1. 时间戳相关

获取当前时间戳

+ (NSTimeInterval)timeBySecond
{
    NSDate* dat = [NSDate dateWithTimeIntervalSinceNow:0];
    return [dat timeIntervalSince1970];
}

+ (NSString *)stringTimeBySecond
{
    return [NSString stringWithFormat:@"%.0f", [[self class] timeBySecond]];
}

NSDate 与时间戳的相互转换

// 将 时间戳 转为 NSDate
convenience init(timeIntervalSince1970 secs: NSTimeInterval)
// 将 NSDate 转为 时间戳
var timeIntervalSince1970: NSTimeInterval { get }

######2. 时间工具类推荐

NSDate+DateTools.h

// Copyright (C) 2014 by Matthew York
//
// Permission is hereby granted, free of charge, to any
// person obtaining a copy of this software and
// associated documentation files (the "Software"), to
// deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the
// Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall
// be included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
// ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

#ifndef DateToolsLocalizedStrings
#define DateToolsLocalizedStrings(key) \
NSLocalizedStringFromTableInBundle(key, @"DateTools", [NSBundle bundleWithPath:[[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"DateTools.bundle"]], nil)
#endif

#import <Foundation/Foundation.h>

static const long long SECONDS_IN_YEAR = 31556900;
static const NSInteger SECONDS_IN_MONTH_28 = 2419200;
static const NSInteger SECONDS_IN_MONTH_29 = 2505600;
static const NSInteger SECONDS_IN_MONTH_30 = 2592000;
static const NSInteger SECONDS_IN_MONTH_31 = 2678400;
static const NSInteger SECONDS_IN_WEEK = 604800;
static const NSInteger SECONDS_IN_DAY = 86400;
static const NSInteger SECONDS_IN_HOUR = 3600;
static const NSInteger SECONDS_IN_MINUTE = 60;
static const NSInteger MILLISECONDS_IN_DAY = 86400000;

@interface NSDate (DateTools)

#pragma mark - Time Ago
+ (NSString*)timeAgoSinceDate:(NSDate*)date;
+ (NSString*)shortTimeAgoSinceDate:(NSDate*)date;
- (NSString*)timeAgoSinceNow;
- (NSString *)shortTimeAgoSinceNow;
- (NSString *)timeAgoSinceDate:(NSDate *)date;
- (NSString *)timeAgoSinceDate:(NSDate *)date numericDates:(BOOL)useNumericDates;
- (NSString *)shortTimeAgoSinceDate:(NSDate *)date;

#pragma mark - Date Components Without Calendar
- (NSInteger)era;
- (NSInteger)year;
- (NSInteger)month;
- (NSInteger)day;
- (NSInteger)hour;
- (NSInteger)minute;
- (NSInteger)second;
- (NSInteger)weekday;
- (NSInteger)weekdayOrdinal;
- (NSInteger)quarter;
- (NSInteger)weekOfMonth;
- (NSInteger)weekOfYear;
- (NSInteger)yearForWeekOfYear;
- (NSInteger)daysInMonth;
- (NSInteger)dayOfYear;
-(NSInteger)daysInYear;
-(BOOL)isInLeapYear;
- (BOOL)isToday;

#pragma mark - Date Components With Calendar

- (NSInteger)eraWithCalendar:(NSCalendar *)calendar;
- (NSInteger)yearWithCalendar:(NSCalendar *)calendar;
- (NSInteger)monthWithCalendar:(NSCalendar *)calendar;
- (NSInteger)dayWithCalendar:(NSCalendar *)calendar;
- (NSInteger)hourWithCalendar:(NSCalendar *)calendar;
- (NSInteger)minuteWithCalendar:(NSCalendar *)calendar;
- (NSInteger)secondWithCalendar:(NSCalendar *)calendar;
- (NSInteger)weekdayWithCalendar:(NSCalendar *)calendar;
- (NSInteger)weekdayOrdinalWithCalendar:(NSCalendar *)calendar;
- (NSInteger)quarterWithCalendar:(NSCalendar *)calendar;
- (NSInteger)weekOfMonthWithCalendar:(NSCalendar *)calendar;
- (NSInteger)weekOfYearWithCalendar:(NSCalendar *)calendar;
- (NSInteger)yearForWeekOfYearWithCalendar:(NSCalendar *)calendar;

#pragma mark - Date Editing
#pragma mark Date By Adding
- (NSDate *)dateByAddingYears:(NSInteger)years;
- (NSDate *)dateByAddingMonths:(NSInteger)months;
- (NSDate *)dateByAddingWeeks:(NSInteger)weeks;
- (NSDate *)dateByAddingDays:(NSInteger)days;
- (NSDate *)dateByAddingHours:(NSInteger)hours;
- (NSDate *)dateByAddingMinutes:(NSInteger)minutes;
- (NSDate *)dateByAddingSeconds:(NSInteger)seconds;
#pragma mark Date By Subtracting
- (NSDate *)dateBySubtractingYears:(NSInteger)years;
- (NSDate *)dateBySubtractingMonths:(NSInteger)months;
- (NSDate *)dateBySubtractingWeeks:(NSInteger)weeks;
- (NSDate *)dateBySubtractingDays:(NSInteger)days;
- (NSDate *)dateBySubtractingHours:(NSInteger)hours;
- (NSDate *)dateBySubtractingMinutes:(NSInteger)minutes;
- (NSDate *)dateBySubtractingSeconds:(NSInteger)seconds;

#pragma mark - Date Comparison
#pragma mark Time From
-(NSInteger)yearsFrom:(NSDate *)date;
-(NSInteger)monthsFrom:(NSDate *)date;
-(NSInteger)weeksFrom:(NSDate *)date;
-(NSInteger)daysFrom:(NSDate *)date;
-(double)hoursFrom:(NSDate *)date;
-(double)minutesFrom:(NSDate *)date;
-(double)secondsFrom:(NSDate *)date;
#pragma mark Time From With Calendar
-(NSInteger)yearsFrom:(NSDate *)date calendar:(NSCalendar *)calendar;
-(NSInteger)monthsFrom:(NSDate *)date calendar:(NSCalendar *)calendar;
-(NSInteger)weeksFrom:(NSDate *)date calendar:(NSCalendar *)calendar;
-(NSInteger)daysFrom:(NSDate *)date calendar:(NSCalendar *)calendar;

#pragma mark Time Until
-(NSInteger)yearsUntil;
-(NSInteger)monthsUntil;
-(NSInteger)weeksUntil;
-(NSInteger)daysUntil;
-(double)hoursUntil;
-(double)minutesUntil;
-(double)secondsUntil;
#pragma mark Time Ago
-(NSInteger)yearsAgo;
-(NSInteger)monthsAgo;
-(NSInteger)weeksAgo;
-(NSInteger)daysAgo;
-(double)hoursAgo;
-(double)minutesAgo;
-(double)secondsAgo;
#pragma mark Earlier Than
-(NSInteger)yearsEarlierThan:(NSDate *)date;
-(NSInteger)monthsEarlierThan:(NSDate *)date;
-(NSInteger)weeksEarlierThan:(NSDate *)date;
-(NSInteger)daysEarlierThan:(NSDate *)date;
-(double)hoursEarlierThan:(NSDate *)date;
-(double)minutesEarlierThan:(NSDate *)date;
-(double)secondsEarlierThan:(NSDate *)date;
#pragma mark Later Than
-(NSInteger)yearsLaterThan:(NSDate *)date;
-(NSInteger)monthsLaterThan:(NSDate *)date;
-(NSInteger)weeksLaterThan:(NSDate *)date;
-(NSInteger)daysLaterThan:(NSDate *)date;
-(double)hoursLaterThan:(NSDate *)date;
-(double)minutesLaterThan:(NSDate *)date;
-(double)secondsLaterThan:(NSDate *)date;
#pragma mark Comparators
-(BOOL)isEarlierThan:(NSDate *)date;
-(BOOL)isLaterThan:(NSDate *)date;
-(BOOL)isEarlierThanOrEqualTo:(NSDate *)date;
-(BOOL)isLaterThanOrEqualTo:(NSDate *)date;

#pragma mark - Formatted Dates
#pragma mark Formatted With Style
-(NSString *)formattedDateWithStyle:(NSDateFormatterStyle)style;
-(NSString *)formattedDateWithStyle:(NSDateFormatterStyle)style timeZone:(NSTimeZone *)timeZone;
-(NSString *)formattedDateWithStyle:(NSDateFormatterStyle)style locale:(NSLocale *)locale;
-(NSString *)formattedDateWithStyle:(NSDateFormatterStyle)style timeZone:(NSTimeZone *)timeZone locale:(NSLocale *)locale;
#pragma mark Formatted With Format
-(NSString *)formattedDateWithFormat:(NSString *)format;
-(NSString *)formattedDateWithFormat:(NSString *)format timeZone:(NSTimeZone *)timeZone;
-(NSString *)formattedDateWithFormat:(NSString *)format locale:(NSLocale *)locale;
-(NSString *)formattedDateWithFormat:(NSString *)format timeZone:(NSTimeZone *)timeZone locale:(NSLocale *)locale;

#pragma mark - Helpers
+(NSString *)defaultCalendarIdentifier;
+ (void)setDefaultCalendarIdentifier:(NSString *)identifier;
@end

NSDate+DateTools.h

// Copyright (C) 2014 by Matthew York
//
// Permission is hereby granted, free of charge, to any
// person obtaining a copy of this software and
// associated documentation files (the "Software"), to
// deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the
// Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall
// be included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
// ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

#import "NSDate+DateTools.h"

typedef NS_ENUM(NSUInteger, DTDateComponent){
    DTDateComponentEra,
    DTDateComponentYear,
    DTDateComponentMonth,
    DTDateComponentDay,
    DTDateComponentHour,
    DTDateComponentMinute,
    DTDateComponentSecond,
    DTDateComponentWeekday,
    DTDateComponentWeekdayOrdinal,
    DTDateComponentQuarter,
    DTDateComponentWeekOfMonth,
    DTDateComponentWeekOfYear,
    DTDateComponentYearForWeekOfYear,
    DTDateComponentDayOfYear
};

static const unsigned int allCalendarUnitFlags = NSYearCalendarUnit | NSQuarterCalendarUnit | NSMonthCalendarUnit | NSWeekOfYearCalendarUnit | NSWeekOfMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit | NSEraCalendarUnit | NSWeekdayCalendarUnit | NSWeekdayOrdinalCalendarUnit | NSWeekCalendarUnit;

static NSString *defaultCalendarIdentifier = nil;
static NSCalendar *implicitCalendar = nil;

@implementation NSDate (DateTools)

+ (void)load {
    [self setDefaultCalendarIdentifier:NSGregorianCalendar];
}

#pragma mark - Time Ago

/**
 *  Takes in a date and returns a string with the most convenient unit of time representing
 *  how far in the past that date is from now.
 *
 *  @param NSDate - Date to be measured from now
 *
 *  @return NSString - Formatted return string
 */
+ (NSString*)timeAgoSinceDate:(NSDate*)date{
    return [date timeAgoSinceDate:[NSDate date]];
}

/**
 *  Takes in a date and returns a shortened string with the most convenient unit of time representing
 *  how far in the past that date is from now.
 *
 *  @param NSDate - Date to be measured from now
 *
 *  @return NSString - Formatted return string
 */
+ (NSString*)shortTimeAgoSinceDate:(NSDate*)date{
    return [date shortTimeAgoSinceDate:[NSDate date]];
}

/**
 *  Returns a string with the most convenient unit of time representing
 *  how far in the past that date is from now.
 *
 *  @return NSString - Formatted return string
 */
- (NSString*)timeAgoSinceNow{
    return [self timeAgoSinceDate:[NSDate date]];
}

/**
 *  Returns a shortened string with the most convenient unit of time representing
 *  how far in the past that date is from now.
 *
 *  @return NSString - Formatted return string
 */
- (NSString *)shortTimeAgoSinceNow{
    return [self shortTimeAgoSinceDate:[NSDate date]];
}

- (NSString *)timeAgoSinceDate:(NSDate *)date{
    return [self timeAgoSinceDate:date numericDates:NO];
}

- (NSString *)timeAgoSinceDate:(NSDate *)date numericDates:(BOOL)useNumericDates{

    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSUInteger unitFlags = NSMinuteCalendarUnit | NSHourCalendarUnit | NSDayCalendarUnit | NSWeekCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit | NSSecondCalendarUnit;
    NSDate *earliest = [self earlierDate:date];
    NSDate *latest = (earliest == self) ? date : self;
    NSDateComponents *components = [calendar components:unitFlags fromDate:earliest toDate:latest options:0];

    //Not Yet Implemented/Optional
    //The following strings are present in the translation files but lack logic as of 2014.04.05
    //@"Today", @"This week", @"This month", @"This year"
    //and @"This morning", @"This afternoon"

    if (components.year >= 2) {
        return  [self logicLocalizedStringFromFormat:@"%%d %@years ago" withValue:components.year];
    }
    else if (components.year >= 1) {

        if (useNumericDates) {
            return DateToolsLocalizedStrings(@"1 year ago");
        }

        return DateToolsLocalizedStrings(@"Last year");
    }
    else if (components.month >= 2) {
        return [self logicLocalizedStringFromFormat:@"%%d %@months ago" withValue:components.month];
    }
    else if (components.month >= 1) {

        if (useNumericDates) {
            return DateToolsLocalizedStrings(@"1 month ago");
        }

        return DateToolsLocalizedStrings(@"Last month");
    }
    else if (components.weekOfMonth >= 2) {
        return [self logicLocalizedStringFromFormat:@"%%d %@weeks ago" withValue:components.weekOfMonth];
    }
    else if (components.weekOfMonth >= 1) {

        if (useNumericDates) {
            return DateToolsLocalizedStrings(@"1 week ago");
        }

        return DateToolsLocalizedStrings(@"Last week");
    }
    else if (components.day >= 2) {
        return [self logicLocalizedStringFromFormat:@"%%d %@days ago" withValue:components.day];
    }
    else if (components.day >= 1) {

        if (useNumericDates) {
            return DateToolsLocalizedStrings(@"1 day ago");
        }

        return DateToolsLocalizedStrings(@"Yesterday");
    }
    else if (components.hour >= 2) {
        return [self logicLocalizedStringFromFormat:@"%%d %@hours ago" withValue:components.hour];
    }
    else if (components.hour >= 1) {
        return DateToolsLocalizedStrings(@"An hour ago");
    }
    else if (components.minute >= 2) {
        return [self logicLocalizedStringFromFormat:@"%%d %@minutes ago" withValue:components.minute];
    }
    else if (components.minute >= 1) {
        return DateToolsLocalizedStrings(@"A minute ago");
    }
    else if (components.second >= 3) {
        return [self logicLocalizedStringFromFormat:@"%%d %@seconds ago" withValue:components.second];
    }
    else {
        return DateToolsLocalizedStrings(@"Just now");
    }

}

- (NSString *)shortTimeAgoSinceDate:(NSDate *)date{

    //If shortened formatting is requested, drop the "ago" part of the time ago
    //use abbreviated unit names

    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSUInteger unitFlags = NSMinuteCalendarUnit | NSHourCalendarUnit | NSDayCalendarUnit | NSWeekCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit | NSSecondCalendarUnit;
    NSDate *earliest = [self earlierDate:date];
    NSDate *latest = (earliest == self) ? date : self;
    NSDateComponents *components = [calendar components:unitFlags fromDate:earliest toDate:latest options:0];

    if (components.year >= 1) {
        return  [self logicLocalizedStringFromFormat:@"%%d%@y" withValue:components.year];
    }
    else if (components.month >= 1) {
        return [self logicLocalizedStringFromFormat:@"%%d%@M" withValue:components.month];
    }
    else if (components.weekOfMonth >= 1) {
        return [self logicLocalizedStringFromFormat:@"%%d%@w" withValue:components.weekOfMonth];
    }
    else if (components.day >= 1) {
        return [self logicLocalizedStringFromFormat:@"%%d%@d" withValue:components.day];
    }
    else if (components.hour >= 1) {
        return [self logicLocalizedStringFromFormat:@"%%d%@h" withValue:components.hour];
    }
    else if (components.minute >= 1) {
        return [self logicLocalizedStringFromFormat:@"%%d%@m" withValue:components.minute];
    }
    else if (components.second >= 3) {
        return [self logicLocalizedStringFromFormat:@"%%d%@s" withValue:components.second];
    }
    else {
        return [self logicLocalizedStringFromFormat:@"%%d%@s" withValue:components.second];
        //return DateToolsLocalizedStrings(@"Now"); //string not yet translated 2014.04.05
    }

}

- (NSString *) logicLocalizedStringFromFormat:(NSString *)format withValue:(NSInteger)value{
    NSString * localeFormat = [NSString stringWithFormat:format, [self getLocaleFormatUnderscoresWithValue:value]];
    return [NSString stringWithFormat:DateToolsLocalizedStrings(localeFormat), value];
}

- (NSString *)getLocaleFormatUnderscoresWithValue:(double)value{
    NSString *localeCode = [[NSLocale preferredLanguages] objectAtIndex:0];

    // Russian (ru)
    if([localeCode isEqual:@"ru"]) {
        int XY = (int)floor(value) % 100;
        int Y = (int)floor(value) % 10;

        if(Y == 0 || Y > 4 || (XY > 10 && XY < 15)) {
            return @"";
        }

        if(Y > 1 && Y < 5 && (XY < 10 || XY > 20))  {
            return @"_";
        }

        if(Y == 1 && XY != 11) {
            return @"__";
        }
    }

    // Add more languages here, which are have specific translation rules...

    return @"";
}

#pragma mark - Date Components Without Calendar
/**
 *  Returns the era of the receiver. (0 for BC, 1 for AD for Gregorian)
 *
 *  @return NSInteger
 */
- (NSInteger)era{
    return [self componentForDate:self type:DTDateComponentEra calendar:nil];
}

/**
 *  Returns the year of the receiver.
 *
 *  @return NSInteger
 */
- (NSInteger)year{
    return [self componentForDate:self type:DTDateComponentYear calendar:nil];
}

/**
 *  Returns the month of the year of the receiver.
 *
 *  @return NSInteger
 */
- (NSInteger)month{
    return [self componentForDate:self type:DTDateComponentMonth calendar:nil];
}

/**
 *  Returns the day of the month of the receiver.
 *
 *  @return NSInteger
 */
- (NSInteger)day{
    return [self componentForDate:self type:DTDateComponentDay calendar:nil];
}

/**
 *  Returns the hour of the day of the receiver. (0-24)
 *
 *  @return NSInteger
 */
- (NSInteger)hour{
    return [self componentForDate:self type:DTDateComponentHour calendar:nil];
}

/**
 *  Returns the minute of the receiver. (0-59)
 *
 *  @return NSInteger
 */
- (NSInteger)minute{
    return [self componentForDate:self type:DTDateComponentMinute calendar:nil];
}

/**
 *  Returns the second of the receiver. (0-59)
 *
 *  @return NSInteger
 */
- (NSInteger)second{
    return [self componentForDate:self type:DTDateComponentSecond calendar:nil];
}

/**
 *  Returns the day of the week of the receiver.
 *
 *  @return NSInteger
 */
- (NSInteger)weekday{
    return [self componentForDate:self type:DTDateComponentWeekday calendar:nil];
}

/**
 *  Returns the ordinal for the day of the week of the receiver.
 *
 *  @return NSInteger
 */
- (NSInteger)weekdayOrdinal{
    return [self componentForDate:self type:DTDateComponentWeekdayOrdinal calendar:nil];
}

/**
 *  Returns the quarter of the receiver.
 *
 *  @return NSInteger
 */
- (NSInteger)quarter{
    return [self componentForDate:self type:DTDateComponentQuarter calendar:nil];
}

/**
 *  Returns the week of the month of the receiver.
 *
 *  @return NSInteger
 */
- (NSInteger)weekOfMonth{
    return [self componentForDate:self type:DTDateComponentWeekOfMonth calendar:nil];
}

/**
 *  Returns the week of the year of the receiver.
 *
 *  @return NSInteger
 */
- (NSInteger)weekOfYear{
    return [self componentForDate:self type:DTDateComponentWeekOfYear calendar:nil];
}

/**
 *  I honestly don't know much about this value...
 *
 *  @return NSInteger
 */
- (NSInteger)yearForWeekOfYear{
    return [self componentForDate:self type:DTDateComponentYearForWeekOfYear calendar:nil];
}

/**
 *  Returns how many days are in the month of the receiver.
 *
 *  @return NSInteger
 */
- (NSInteger)daysInMonth{
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSRange days = [calendar rangeOfUnit:NSDayCalendarUnit
                                  inUnit:NSMonthCalendarUnit
                                 forDate:self];
    return days.length;
}

/**
 *  Returns the day of the year of the receiver. (1-365 or 1-366 for leap year)
 *
 *  @return NSInteger
 */
- (NSInteger)dayOfYear{
    return [self componentForDate:self type:DTDateComponentDayOfYear calendar:nil];
}

/**
 *  Returns how many days are in the year of the receiver.
 *
 *  @return NSInteger
 */
-(NSInteger)daysInYear{
    if (self.isInLeapYear) {
        return 366;
    }

    return 365;
}

/**
 *  Returns whether the receiver falls in a leap year.
 *
 *  @return NSInteger
 */
-(BOOL)isInLeapYear{
    NSCalendar *calendar = [[self class] implicitCalendar];
    NSDateComponents *dateComponents = [calendar components:allCalendarUnitFlags fromDate:self];

    if (dateComponents.year%400 == 0){
        return YES;
    }
    else if (dateComponents.year%100 == 0){
        return NO;
    }
    else if (dateComponents.year%4 == 0){
        return YES;
    }

    return NO;
}

- (BOOL)isToday {
    NSCalendar *cal = [NSCalendar currentCalendar];
    NSDateComponents *components = [cal components:(NSEraCalendarUnit|NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit) fromDate:[NSDate date]];
    NSDate *today = [cal dateFromComponents:components];
    components = [cal components:(NSEraCalendarUnit|NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit) fromDate:self];
    NSDate *otherDate = [cal dateFromComponents:components];

    return [today isEqualToDate:otherDate];
}

#pragma mark - Date Components With Calendar
/**
 *  Returns the era of the receiver from a given calendar
 *
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - represents the era (0 for BC, 1 for AD for Gregorian)
 */
- (NSInteger)eraWithCalendar:(NSCalendar *)calendar{
    return [self componentForDate:self type:DTDateComponentEra calendar:calendar];
}

/**
 *  Returns the year of the receiver from a given calendar
 *
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - represents the year as an integer
 */
- (NSInteger)yearWithCalendar:(NSCalendar *)calendar{
    return [self componentForDate:self type:DTDateComponentYear calendar:calendar];
}

/**
 *  Returns the month of the receiver from a given calendar
 *
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - represents the month as an integer
 */
- (NSInteger)monthWithCalendar:(NSCalendar *)calendar{
    return [self componentForDate:self type:DTDateComponentMonth calendar:calendar];
}

/**
 *  Returns the day of the month of the receiver from a given calendar
 *
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - represents the day of the month as an integer
 */
- (NSInteger)dayWithCalendar:(NSCalendar *)calendar{
    return [self componentForDate:self type:DTDateComponentDay calendar:calendar];
}

/**
 *  Returns the hour of the day of the receiver from a given calendar
 *
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - represents the hour of the day as an integer
 */
- (NSInteger)hourWithCalendar:(NSCalendar *)calendar{
    return [self componentForDate:self type:DTDateComponentHour calendar:calendar];
}

/**
 *  Returns the minute of the hour of the receiver from a given calendar
 *
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - represents the minute of the hour as an integer
 */
- (NSInteger)minuteWithCalendar:(NSCalendar *)calendar{
    return [self componentForDate:self type:DTDateComponentMinute calendar:calendar];
}

/**
 *  Returns the second of the receiver from a given calendar
 *
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - represents the second as an integer
 */
- (NSInteger)secondWithCalendar:(NSCalendar *)calendar{
    return [self componentForDate:self type:DTDateComponentSecond calendar:calendar];
}

/**
 *  Returns the weekday of the receiver from a given calendar
 *
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - represents the weekday as an integer
 */
- (NSInteger)weekdayWithCalendar:(NSCalendar *)calendar{
    return [self componentForDate:self type:DTDateComponentWeekday calendar:calendar];
}

/**
 *  Returns the weekday ordinal of the receiver from a given calendar
 *
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - represents the weekday ordinal as an integer
 */
- (NSInteger)weekdayOrdinalWithCalendar:(NSCalendar *)calendar{
    return [self componentForDate:self type:DTDateComponentWeekdayOrdinal calendar:calendar];
}

/**
 *  Returns the quarter of the receiver from a given calendar
 *
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - represents the quarter as an integer
 */
- (NSInteger)quarterWithCalendar:(NSCalendar *)calendar{
    return [self componentForDate:self type:DTDateComponentQuarter calendar:calendar];
}

/**
 *  Returns the week of the month of the receiver from a given calendar
 *
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - represents the week of the month as an integer
 */
- (NSInteger)weekOfMonthWithCalendar:(NSCalendar *)calendar{
    return [self componentForDate:self type:DTDateComponentWeekOfMonth calendar:calendar];
}

/**
 *  Returns the week of the year of the receiver from a given calendar
 *
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - represents the week of the year as an integer
 */
- (NSInteger)weekOfYearWithCalendar:(NSCalendar *)calendar{
    return [self componentForDate:self type:DTDateComponentWeekOfYear calendar:calendar];
}

/**
 *  Returns the year for week of the year (???) of the receiver from a given calendar
 *
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - represents the year for week of the year as an integer
 */
- (NSInteger)yearForWeekOfYearWithCalendar:(NSCalendar *)calendar{
    return [self componentForDate:self type:DTDateComponentYearForWeekOfYear calendar:calendar];
}

/**
 *  Returns the day of the year of the receiver from a given calendar
 *
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - represents the day of the year as an integer
 */
- (NSInteger)dayOfYearWithCalendar:(NSCalendar *)calendar{
    return [self componentForDate:self type:DTDateComponentDayOfYear calendar:calendar];
}

/**
 *  Takes in a date, calendar and desired date component and returns the desired NSInteger
 *  representation for that component
 *
 *  @param date      NSDate - The date to be be mined for a desired component
 *  @param component DTDateComponent - The desired component (i.e. year, day, week, etc)
 *  @param calendar  NSCalendar - The calendar to be used in the processing (Defaults to Gregorian)
 *
 *  @return NSInteger
 */
-(NSInteger)componentForDate:(NSDate *)date type:(DTDateComponent)component calendar:(NSCalendar *)calendar{
    if (!calendar) {
        calendar = [[self class] implicitCalendar];
    }

    unsigned int unitFlags = 0;

    if (component == DTDateComponentYearForWeekOfYear) {
       unitFlags = NSYearCalendarUnit | NSQuarterCalendarUnit | NSMonthCalendarUnit | NSWeekOfYearCalendarUnit | NSWeekOfMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit | NSEraCalendarUnit | NSWeekdayCalendarUnit | NSWeekdayOrdinalCalendarUnit | NSWeekCalendarUnit | NSYearForWeekOfYearCalendarUnit;
    }
    else {
        unitFlags = allCalendarUnitFlags;
    }

    NSDateComponents *dateComponents = [calendar components:unitFlags fromDate:date];

    switch (component) {
        case DTDateComponentEra:
            return [dateComponents era];
        case DTDateComponentYear:
            return [dateComponents year];
        case DTDateComponentMonth:
            return [dateComponents month];
        case DTDateComponentDay:
            return [dateComponents day];
        case DTDateComponentHour:
            return [dateComponents hour];
        case DTDateComponentMinute:
            return [dateComponents minute];
        case DTDateComponentSecond:
            return [dateComponents second];
        case DTDateComponentWeekday:
            return [dateComponents weekday];
        case DTDateComponentWeekdayOrdinal:
            return [dateComponents weekdayOrdinal];
        case DTDateComponentQuarter:
            return [dateComponents quarter];
        case DTDateComponentWeekOfMonth:
            return [dateComponents weekOfMonth];
        case DTDateComponentWeekOfYear:
            return [dateComponents weekOfYear];
        case DTDateComponentYearForWeekOfYear:
            return [dateComponents yearForWeekOfYear];
        case DTDateComponentDayOfYear:
            return [calendar ordinalityOfUnit:NSDayCalendarUnit inUnit:NSYearCalendarUnit forDate:date];
        default:
            break;
    }

    return 0;
}

#pragma mark - Date Editing
#pragma mark Date By Adding
/**
 *  Returns a date representing the receivers date shifted later by the provided number of years.
 *
 *  @param years NSInteger - Number of years to add
 *
 *  @return NSDate - Date modified by the number of desired years
 */
- (NSDate *)dateByAddingYears:(NSInteger)years{
    NSCalendar *calendar = [[self class] implicitCalendar];
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setYear:years];

    return [calendar dateByAddingComponents:components toDate:self options:0];
}

/**
 *  Returns a date representing the receivers date shifted later by the provided number of months.
 *
 *  @param years NSInteger - Number of months to add
 *
 *  @return NSDate - Date modified by the number of desired months
 */
- (NSDate *)dateByAddingMonths:(NSInteger)months{
    NSCalendar *calendar = [[self class] implicitCalendar];
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setMonth:months];

    return [calendar dateByAddingComponents:components toDate:self options:0];
}

/**
 *  Returns a date representing the receivers date shifted later by the provided number of weeks.
 *
 *  @param years NSInteger - Number of weeks to add
 *
 *  @return NSDate - Date modified by the number of desired weeks
 */
- (NSDate *)dateByAddingWeeks:(NSInteger)weeks{
    NSCalendar *calendar = [[self class] implicitCalendar];
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setWeekOfMonth:weeks];

    return [calendar dateByAddingComponents:components toDate:self options:0];
}

/**
 *  Returns a date representing the receivers date shifted later by the provided number of days.
 *
 *  @param years NSInteger - Number of days to add
 *
 *  @return NSDate - Date modified by the number of desired days
 */
- (NSDate *)dateByAddingDays:(NSInteger)days{
    NSCalendar *calendar = [[self class] implicitCalendar];
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setDay:days];

    return [calendar dateByAddingComponents:components toDate:self options:0];
}

/**
 *  Returns a date representing the receivers date shifted later by the provided number of hours.
 *
 *  @param years NSInteger - Number of hours to add
 *
 *  @return NSDate - Date modified by the number of desired hours
 */
- (NSDate *)dateByAddingHours:(NSInteger)hours{
    NSCalendar *calendar = [[self class] implicitCalendar];
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setHour:hours];

    return [calendar dateByAddingComponents:components toDate:self options:0];
}

/**
 *  Returns a date representing the receivers date shifted later by the provided number of minutes.
 *
 *  @param years NSInteger - Number of minutes to add
 *
 *  @return NSDate - Date modified by the number of desired minutes
 */
- (NSDate *)dateByAddingMinutes:(NSInteger)minutes{
    NSCalendar *calendar = [[self class] implicitCalendar];
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setMinute:minutes];

    return [calendar dateByAddingComponents:components toDate:self options:0];
}

/**
 *  Returns a date representing the receivers date shifted later by the provided number of seconds.
 *
 *  @param years NSInteger - Number of seconds to add
 *
 *  @return NSDate - Date modified by the number of desired seconds
 */
- (NSDate *)dateByAddingSeconds:(NSInteger)seconds{
    NSCalendar *calendar = [[self class] implicitCalendar];
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setSecond:seconds];

    return [calendar dateByAddingComponents:components toDate:self options:0];
}

#pragma mark Date By Subtracting
/**
 *  Returns a date representing the receivers date shifted earlier by the provided number of years.
 *
 *  @param years NSInteger - Number of years to subtract
 *
 *  @return NSDate - Date modified by the number of desired years
 */
- (NSDate *)dateBySubtractingYears:(NSInteger)years{
    NSCalendar *calendar = [[self class] implicitCalendar];
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setYear:-1*years];

    return [calendar dateByAddingComponents:components toDate:self options:0];
}

/**
 *  Returns a date representing the receivers date shifted earlier by the provided number of months.
 *
 *  @param years NSInteger - Number of months to subtract
 *
 *  @return NSDate - Date modified by the number of desired months
 */
- (NSDate *)dateBySubtractingMonths:(NSInteger)months{
    NSCalendar *calendar = [[self class] implicitCalendar];
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setMonth:-1*months];

    return [calendar dateByAddingComponents:components toDate:self options:0];
}

/**
 *  Returns a date representing the receivers date shifted earlier by the provided number of weeks.
 *
 *  @param years NSInteger - Number of weeks to subtract
 *
 *  @return NSDate - Date modified by the number of desired weeks
 */
- (NSDate *)dateBySubtractingWeeks:(NSInteger)weeks{
    NSCalendar *calendar = [[self class] implicitCalendar];
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setWeekOfMonth:-1*weeks];

    return [calendar dateByAddingComponents:components toDate:self options:0];
}

/**
 *  Returns a date representing the receivers date shifted earlier by the provided number of days.
 *
 *  @param years NSInteger - Number of days to subtract
 *
 *  @return NSDate - Date modified by the number of desired days
 */
- (NSDate *)dateBySubtractingDays:(NSInteger)days{
    NSCalendar *calendar = [[self class] implicitCalendar];
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setDay:-1*days];

    return [calendar dateByAddingComponents:components toDate:self options:0];
}

/**
 *  Returns a date representing the receivers date shifted earlier by the provided number of hours.
 *
 *  @param years NSInteger - Number of hours to subtract
 *
 *  @return NSDate - Date modified by the number of desired hours
 */
- (NSDate *)dateBySubtractingHours:(NSInteger)hours{
    NSCalendar *calendar = [[self class] implicitCalendar];
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setHour:-1*hours];

    return [calendar dateByAddingComponents:components toDate:self options:0];
}

/**
 *  Returns a date representing the receivers date shifted earlier by the provided number of minutes.
 *
 *  @param years NSInteger - Number of minutes to subtract
 *
 *  @return NSDate - Date modified by the number of desired minutes
 */
- (NSDate *)dateBySubtractingMinutes:(NSInteger)minutes{
    NSCalendar *calendar = [[self class] implicitCalendar];
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setMinute:-1*minutes];

    return [calendar dateByAddingComponents:components toDate:self options:0];
}

/**
 *  Returns a date representing the receivers date shifted earlier by the provided number of seconds.
 *
 *  @param years NSInteger - Number of seconds to subtract
 *
 *  @return NSDate - Date modified by the number of desired seconds
 */
- (NSDate *)dateBySubtractingSeconds:(NSInteger)seconds{
    NSCalendar *calendar = [[self class] implicitCalendar];
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setSecond:-1*seconds];

    return [calendar dateByAddingComponents:components toDate:self options:0];
}

#pragma mark - Date Comparison
#pragma mark Time From
/**
 *  Returns an NSInteger representing the amount of time in years between the receiver and the provided date.
 *  If the receiver is earlier than the provided date, the returned value will be negative.
 *  Uses the default Gregorian calendar
 *
 *  @param date NSDate - The provided date for comparison
 *
 *  @return NSInteger - The NSInteger representation of the years between receiver and provided date
 */
-(NSInteger)yearsFrom:(NSDate *)date{
    return [self yearsFrom:date calendar:nil];
}

/**
 *  Returns an NSInteger representing the amount of time in months between the receiver and the provided date.
 *  If the receiver is earlier than the provided date, the returned value will be negative.
 *  Uses the default Gregorian calendar
 *
 *  @param date NSDate - The provided date for comparison
 *
 *  @return NSInteger - The NSInteger representation of the years between receiver and provided date
 */
-(NSInteger)monthsFrom:(NSDate *)date{
    return [self monthsFrom:date calendar:nil];
}

/**
 *  Returns an NSInteger representing the amount of time in weeks between the receiver and the provided date.
 *  If the receiver is earlier than the provided date, the returned value will be negative.
 *  Uses the default Gregorian calendar
 *
 *  @param date NSDate - The provided date for comparison
 *
 *  @return NSInteger - The double representation of the weeks between receiver and provided date
 */
-(NSInteger)weeksFrom:(NSDate *)date{
    return [self weeksFrom:date calendar:nil];
}

/**
 *  Returns an NSInteger representing the amount of time in days between the receiver and the provided date.
 *  If the receiver is earlier than the provided date, the returned value will be negative.
 *  Uses the default Gregorian calendar
 *
 *  @param date NSDate - The provided date for comparison
 *
 *  @return NSInteger - The double representation of the days between receiver and provided date
 */
-(NSInteger)daysFrom:(NSDate *)date{
    return [self daysFrom:date calendar:nil];
}

/**
 *  Returns an NSInteger representing the amount of time in hours between the receiver and the provided date.
 *  If the receiver is earlier than the provided date, the returned value will be negative.
 *
 *  @param date NSDate - The provided date for comparison
 *
 *  @return double - The double representation of the hours between receiver and provided date
 */
-(double)hoursFrom:(NSDate *)date{
    return ([self timeIntervalSinceDate:date])/SECONDS_IN_HOUR;
}

/**
 *  Returns an NSInteger representing the amount of time in minutes between the receiver and the provided date.
 *  If the receiver is earlier than the provided date, the returned value will be negative.
 *
 *  @param date NSDate - The provided date for comparison
 *
 *  @return double - The double representation of the minutes between receiver and provided date
 */
-(double)minutesFrom:(NSDate *)date{
    return ([self timeIntervalSinceDate:date])/SECONDS_IN_MINUTE;
}

/**
 *  Returns an NSInteger representing the amount of time in seconds between the receiver and the provided date.
 *  If the receiver is earlier than the provided date, the returned value will be negative.
 *
 *  @param date NSDate - The provided date for comparison
 *
 *  @return double - The double representation of the seconds between receiver and provided date
 */
-(double)secondsFrom:(NSDate *)date{
    return [self timeIntervalSinceDate:date];
}

#pragma mark Time From With Calendar
/**
 *  Returns an NSInteger representing the amount of time in years between the receiver and the provided date.
 *  If the receiver is earlier than the provided date, the returned value will be negative.
 *
 *  @param date     NSDate - The provided date for comparison
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - The double representation of the years between receiver and provided date
 */
-(NSInteger)yearsFrom:(NSDate *)date calendar:(NSCalendar *)calendar{
    if (!calendar) {
        calendar = [[self class] implicitCalendar];
    }

    NSDate *earliest = [self earlierDate:date];
    NSDate *latest = (earliest == self) ? date : self;
    NSInteger multiplier = (earliest == self) ? -1 : 1;
    NSDateComponents *components = [calendar components:NSYearCalendarUnit fromDate:earliest toDate:latest options:0];
    return multiplier*components.year;
}

/**
 *  Returns an NSInteger representing the amount of time in months between the receiver and the provided date.
 *  If the receiver is earlier than the provided date, the returned value will be negative.
 *
 *  @param date     NSDate - The provided date for comparison
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - The double representation of the months between receiver and provided date
 */
-(NSInteger)monthsFrom:(NSDate *)date calendar:(NSCalendar *)calendar{
    if (!calendar) {
        calendar = [[self class] implicitCalendar];
    }

    NSDate *earliest = [self earlierDate:date];
    NSDate *latest = (earliest == self) ? date : self;
    NSInteger multiplier = (earliest == self) ? -1 : 1;
    NSDateComponents *components = [calendar components:allCalendarUnitFlags fromDate:earliest toDate:latest options:0];
    return multiplier*(components.month + 12*components.year);
}

/**
 *  Returns an NSInteger representing the amount of time in weeks between the receiver and the provided date.
 *  If the receiver is earlier than the provided date, the returned value will be negative.
 *
 *  @param date     NSDate - The provided date for comparison
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - The double representation of the weeks between receiver and provided date
 */
-(NSInteger)weeksFrom:(NSDate *)date calendar:(NSCalendar *)calendar{
    if (!calendar) {
        calendar = [[self class] implicitCalendar];
    }

    NSDate *earliest = [self earlierDate:date];
    NSDate *latest = (earliest == self) ? date : self;
    NSInteger multiplier = (earliest == self) ? -1 : 1;
    NSDateComponents *components = [calendar components:NSWeekCalendarUnit fromDate:earliest toDate:latest options:0];
    return multiplier*components.weekOfMonth;
}

/**
 *  Returns an NSInteger representing the amount of time in days between the receiver and the provided date.
 *  If the receiver is earlier than the provided date, the returned value will be negative.
 *
 *  @param date     NSDate - The provided date for comparison
 *  @param calendar NSCalendar - The calendar to be used in the calculation
 *
 *  @return NSInteger - The double representation of the days between receiver and provided date
 */
-(NSInteger)daysFrom:(NSDate *)date calendar:(NSCalendar *)calendar{
    if (!calendar) {
        calendar = [[self class] implicitCalendar];
    }

    NSDate *earliest = [self earlierDate:date];
    NSDate *latest = (earliest == self) ? date : self;
    NSInteger multiplier = (earliest == self) ? -1 : 1;
    NSDateComponents *components = [calendar components:NSDayCalendarUnit fromDate:earliest toDate:latest options:0];
    return multiplier*components.day;
}

#pragma mark Time Until
/**
 *  Returns the number of years until the receiver's date. Returns 0 if the receiver is the same or earlier than now.
 *
 *  @return NSInteger representiation of years
 */
-(NSInteger)yearsUntil{
    return [self yearsLaterThan:[NSDate date]];
}

/**
 *  Returns the number of months until the receiver's date. Returns 0 if the receiver is the same or earlier than now.
 *
 *  @return NSInteger representiation of months
 */
-(NSInteger)monthsUntil{
    return [self monthsLaterThan:[NSDate date]];
}

/**
 *  Returns the number of weeks until the receiver's date. Returns 0 if the receiver is the same or earlier than now.
 *
 *  @return NSInteger representiation of weeks
 */
-(NSInteger)weeksUntil{
    return [self weeksLaterThan:[NSDate date]];
}

/**
 *  Returns the number of days until the receiver's date. Returns 0 if the receiver is the same or earlier than now.
 *
 *  @return NSInteger representiation of days
 */
-(NSInteger)daysUntil{
    return [self daysLaterThan:[NSDate date]];
}

/**
 *  Returns the number of hours until the receiver's date. Returns 0 if the receiver is the same or earlier than now.
 *
 *  @return double representiation of hours
 */
-(double)hoursUntil{
    return [self hoursLaterThan:[NSDate date]];
}

/**
 *  Returns the number of minutes until the receiver's date. Returns 0 if the receiver is the same or earlier than now.
 *
 *  @return double representiation of minutes
 */
-(double)minutesUntil{
    return [self minutesLaterThan:[NSDate date]];
}

/**
 *  Returns the number of seconds until the receiver's date. Returns 0 if the receiver is the same or earlier than now.
 *
 *  @return double representiation of seconds
 */
-(double)secondsUntil{
    return [self secondsLaterThan:[NSDate date]];
}

#pragma mark Time Ago
/**
 *  Returns the number of years the receiver's date is earlier than now. Returns 0 if the receiver is the same or later than now.
 *
 *  @return NSInteger representiation of years
 */
-(NSInteger)yearsAgo{
    return [self yearsEarlierThan:[NSDate date]];
}

/**
 *  Returns the number of months the receiver's date is earlier than now. Returns 0 if the receiver is the same or later than now.
 *
 *  @return NSInteger representiation of months
 */
-(NSInteger)monthsAgo{
    return [self monthsEarlierThan:[NSDate date]];
}

/**
 *  Returns the number of weeks the receiver's date is earlier than now. Returns 0 if the receiver is the same or later than now.
 *
 *  @return NSInteger representiation of weeks
 */
-(NSInteger)weeksAgo{
    return [self weeksEarlierThan:[NSDate date]];
}

/**
 *  Returns the number of days the receiver's date is earlier than now. Returns 0 if the receiver is the same or later than now.
 *
 *  @return NSInteger representiation of days
 */
-(NSInteger)daysAgo{
    return [self daysEarlierThan:[NSDate date]];
}

/**
 *  Returns the number of hours the receiver's date is earlier than now. Returns 0 if the receiver is the same or later than now.
 *
 *  @return double representiation of hours
 */
-(double)hoursAgo{
    return [self hoursEarlierThan:[NSDate date]];
}

/**
 *  Returns the number of minutes the receiver's date is earlier than now. Returns 0 if the receiver is the same or later than now.
 *
 *  @return double representiation of minutes
 */
-(double)minutesAgo{
    return [self minutesEarlierThan:[NSDate date]];
}

/**
 *  Returns the number of seconds the receiver's date is earlier than now. Returns 0 if the receiver is the same or later than now.
 *
 *  @return double representiation of seconds
 */
-(double)secondsAgo{
    return [self secondsEarlierThan:[NSDate date]];
}

#pragma mark Earlier Than
/**
 *  Returns the number of years the receiver's date is earlier than the provided comparison date.
 *  Returns 0 if the receiver's date is later than or equal to the provided comparison date.
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return NSInteger representing the number of years
 */
-(NSInteger)yearsEarlierThan:(NSDate *)date{
    return ABS(MIN([self yearsFrom:date], 0));
}

/**
 *  Returns the number of months the receiver's date is earlier than the provided comparison date.
 *  Returns 0 if the receiver's date is later than or equal to the provided comparison date.
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return NSInteger representing the number of months
 */
-(NSInteger)monthsEarlierThan:(NSDate *)date{
    return ABS(MIN([self monthsFrom:date], 0));
}

/**
 *  Returns the number of weeks the receiver's date is earlier than the provided comparison date.
 *  Returns 0 if the receiver's date is later than or equal to the provided comparison date.
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return NSInteger representing the number of weeks
 */
-(NSInteger)weeksEarlierThan:(NSDate *)date{
    return ABS(MIN([self weeksFrom:date], 0));
}

/**
 *  Returns the number of days the receiver's date is earlier than the provided comparison date.
 *  Returns 0 if the receiver's date is later than or equal to the provided comparison date.
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return NSInteger representing the number of days
 */
-(NSInteger)daysEarlierThan:(NSDate *)date{
    return ABS(MIN([self daysFrom:date], 0));
}

/**
 *  Returns the number of hours the receiver's date is earlier than the provided comparison date.
 *  Returns 0 if the receiver's date is later than or equal to the provided comparison date.
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return double representing the number of hours
 */
-(double)hoursEarlierThan:(NSDate *)date{
    return ABS(MIN([self hoursFrom:date], 0));
}

/**
 *  Returns the number of minutes the receiver's date is earlier than the provided comparison date.
 *  Returns 0 if the receiver's date is later than or equal to the provided comparison date.
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return double representing the number of minutes
 */
-(double)minutesEarlierThan:(NSDate *)date{
    return ABS(MIN([self minutesFrom:date], 0));
}

/**
 *  Returns the number of seconds the receiver's date is earlier than the provided comparison date.
 *  Returns 0 if the receiver's date is later than or equal to the provided comparison date.
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return double representing the number of seconds
 */
-(double)secondsEarlierThan:(NSDate *)date{
    return ABS(MIN([self secondsFrom:date], 0));
}

#pragma mark Later Than
/**
 *  Returns the number of years the receiver's date is later than the provided comparison date.
 *  Returns 0 if the receiver's date is earlier than or equal to the provided comparison date.
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return NSInteger representing the number of years
 */
-(NSInteger)yearsLaterThan:(NSDate *)date{
    return MAX([self yearsFrom:date], 0);
}

/**
 *  Returns the number of months the receiver's date is later than the provided comparison date.
 *  Returns 0 if the receiver's date is earlier than or equal to the provided comparison date.
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return NSInteger representing the number of months
 */
-(NSInteger)monthsLaterThan:(NSDate *)date{
    return MAX([self monthsFrom:date], 0);
}

/**
 *  Returns the number of weeks the receiver's date is later than the provided comparison date.
 *  Returns 0 if the receiver's date is earlier than or equal to the provided comparison date.
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return NSInteger representing the number of weeks
 */
-(NSInteger)weeksLaterThan:(NSDate *)date{
    return MAX([self weeksFrom:date], 0);
}

/**
 *  Returns the number of days the receiver's date is later than the provided comparison date.
 *  Returns 0 if the receiver's date is earlier than or equal to the provided comparison date.
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return NSInteger representing the number of days
 */
-(NSInteger)daysLaterThan:(NSDate *)date{
    return MAX([self daysFrom:date], 0);
}

/**
 *  Returns the number of hours the receiver's date is later than the provided comparison date.
 *  Returns 0 if the receiver's date is earlier than or equal to the provided comparison date.
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return double representing the number of hours
 */
-(double)hoursLaterThan:(NSDate *)date{
    return MAX([self hoursFrom:date], 0);
}

/**
 *  Returns the number of minutes the receiver's date is later than the provided comparison date.
 *  Returns 0 if the receiver's date is earlier than or equal to the provided comparison date.
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return double representing the number of minutes
 */
-(double)minutesLaterThan:(NSDate *)date{
    return MAX([self minutesFrom:date], 0);
}

/**
 *  Returns the number of seconds the receiver's date is later than the provided comparison date.
 *  Returns 0 if the receiver's date is earlier than or equal to the provided comparison date.
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return double representing the number of seconds
 */
-(double)secondsLaterThan:(NSDate *)date{
    return MAX([self secondsFrom:date], 0);
}

#pragma mark Comparators
/**
 *  Returns a YES if receiver is earlier than provided comparison date, otherwise returns NO
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return BOOL representing comparison result
 */
-(BOOL)isEarlierThan:(NSDate *)date{
    if (self.timeIntervalSince1970 < date.timeIntervalSince1970) {
        return YES;
    }
    return NO;
}

/**
 *  Returns a YES if receiver is later than provided comparison date, otherwise returns NO
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return BOOL representing comparison result
 */
-(BOOL)isLaterThan:(NSDate *)date{
    if (self.timeIntervalSince1970 > date.timeIntervalSince1970) {
        return YES;
    }
    return NO;
}

/**
 *  Returns a YES if receiver is earlier than or equal to the provided comparison date, otherwise returns NO
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return BOOL representing comparison result
 */
-(BOOL)isEarlierThanOrEqualTo:(NSDate *)date{
    if (self.timeIntervalSince1970 <= date.timeIntervalSince1970) {
        return YES;
    }
    return NO;
}

/**
 *  Returns a YES if receiver is later than or equal to provided comparison date, otherwise returns NO
 *
 *  @param date NSDate - Provided date for comparison
 *
 *  @return BOOL representing comparison result
 */
-(BOOL)isLaterThanOrEqualTo:(NSDate *)date{
    if (self.timeIntervalSince1970 >= date.timeIntervalSince1970) {
        return YES;
    }
    return NO;
}

#pragma mark - Formatted Dates
#pragma mark Formatted With Style
/**
 *  Convenience method that returns a formatted string representing the receiver's date formatted to a given style
 *
 *  @param style NSDateFormatterStyle - Desired date formatting style
 *
 *  @return NSString representing the formatted date string
 */
-(NSString *)formattedDateWithStyle:(NSDateFormatterStyle)style{
    return [self formattedDateWithStyle:style timeZone:[NSTimeZone systemTimeZone] locale:[NSLocale autoupdatingCurrentLocale]];
}

/**
 *  Convenience method that returns a formatted string representing the receiver's date formatted to a given style and time zone
 *
 *  @param style    NSDateFormatterStyle - Desired date formatting style
 *  @param timeZone NSTimeZone - Desired time zone
 *
 *  @return NSString representing the formatted date string
 */
-(NSString *)formattedDateWithStyle:(NSDateFormatterStyle)style timeZone:(NSTimeZone *)timeZone{
    return [self formattedDateWithStyle:style timeZone:timeZone locale:[NSLocale autoupdatingCurrentLocale]];
}

/**
 *  Convenience method that returns a formatted string representing the receiver's date formatted to a given style and locale
 *
 *  @param style  NSDateFormatterStyle - Desired date formatting style
 *  @param locale NSLocale - Desired locale
 *
 *  @return NSString representing the formatted date string
 */
-(NSString *)formattedDateWithStyle:(NSDateFormatterStyle)style locale:(NSLocale *)locale{
    return [self formattedDateWithStyle:style timeZone:[NSTimeZone systemTimeZone] locale:locale];
}

/**
 *  Convenience method that returns a formatted string representing the receiver's date formatted to a given style, time zone and locale
 *
 *  @param style    NSDateFormatterStyle - Desired date formatting style
 *  @param timeZone NSTimeZone - Desired time zone
 *  @param locale   NSLocale - Desired locale
 *
 *  @return NSString representing the formatted date string
 */
-(NSString *)formattedDateWithStyle:(NSDateFormatterStyle)style timeZone:(NSTimeZone *)timeZone locale:(NSLocale *)locale{
    static NSDateFormatter *formatter = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        formatter = [[NSDateFormatter alloc] init];
    });

    [formatter setDateStyle:style];
    [formatter setTimeZone:timeZone];
    [formatter setLocale:locale];
    return [formatter stringFromDate:self];
}

#pragma mark Formatted With Format
/**
 *  Convenience method that returns a formatted string representing the receiver's date formatted to a given date format
 *
 *  @param format NSString - String representing the desired date format
 *
 *  @return NSString representing the formatted date string
 */
-(NSString *)formattedDateWithFormat:(NSString *)format{
    return [self formattedDateWithFormat:format timeZone:[NSTimeZone systemTimeZone] locale:[NSLocale autoupdatingCurrentLocale]];
}

/**
 *  Convenience method that returns a formatted string representing the receiver's date formatted to a given date format and time zone
 *
 *  @param format   NSString - String representing the desired date format
 *  @param timeZone NSTimeZone - Desired time zone
 *
 *  @return NSString representing the formatted date string
 */
-(NSString *)formattedDateWithFormat:(NSString *)format timeZone:(NSTimeZone *)timeZone{
    return [self formattedDateWithFormat:format timeZone:timeZone locale:[NSLocale autoupdatingCurrentLocale]];
}

/**
 *  Convenience method that returns a formatted string representing the receiver's date formatted to a given date format and locale
 *
 *  @param format NSString - String representing the desired date format
 *  @param locale NSLocale - Desired locale
 *
 *  @return NSString representing the formatted date string
 */
-(NSString *)formattedDateWithFormat:(NSString *)format locale:(NSLocale *)locale{
    return [self formattedDateWithFormat:format timeZone:[NSTimeZone systemTimeZone] locale:locale];
}

/**
 *  Convenience method that returns a formatted string representing the receiver's date formatted to a given date format, time zone and locale
 *
 *  @param format   NSString - String representing the desired date format
 *  @param timeZone NSTimeZone - Desired time zone
 *  @param locale   NSLocale - Desired locale
 *
 *  @return NSString representing the formatted date string
 */
-(NSString *)formattedDateWithFormat:(NSString *)format timeZone:(NSTimeZone *)timeZone locale:(NSLocale *)locale{
    static NSDateFormatter *formatter = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        formatter = [[NSDateFormatter alloc] init];
    });

    [formatter setDateFormat:format];
    [formatter setTimeZone:timeZone];
    [formatter setLocale:locale];
    return [formatter stringFromDate:self];
}

#pragma mark - Helpers
/**
 *  Class method that returns whether the given year is a leap year for the Gregorian Calendar
 *  Returns YES if year is a leap year, otherwise returns NO
 *
 *  @param year NSInteger - Year to evaluate
 *
 *  @return BOOL evaluation of year
 */
+(BOOL)isLeapYear:(NSInteger)year{
    if (year*400){
        return YES;
    }
    else if (year%100){
        return NO;
    }
    else if (year%4){
        return YES;
    }

    return NO;
}

/**
 *  Retrieves the default calendar identifier used for all non-calendar-specified operations
 *
 *  @return NSString - NSCalendarIdentifier
 */
+(NSString *)defaultCalendarIdentifier {
    return defaultCalendarIdentifier;
}

/**
 *  Sets the default calendar identifier used for all non-calendar-specified operations
 *
 *  @param identifier NSString - NSCalendarIdentifier
 */
+ (void)setDefaultCalendarIdentifier:(NSString *)identifier {
    defaultCalendarIdentifier = [identifier copy];
    implicitCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:defaultCalendarIdentifier ?: NSGregorianCalendar];
}

/**
 *  Retrieves a default NSCalendar instance, based on the value of defaultCalendarSetting
 *
 *  @return NSCalendar The current implicit calendar
 */
+ (NSCalendar *)implicitCalendar {
    return implicitCalendar;
}

@end

######3. 时间显示格式

格式	显示
dd/MM/yyyy hh:mm a	30/03/2015 4:00 PM
MMM dd,YYYY	Apr 11,2015
EEE MMM dd HH:mm:ss Z yyyy	Thu Apr 09 14:37:22 +0800 2015

#####4. 时间工具方法

从 NSString -> NSDate

+ (NSDate *)getDateFromString:(NSString *)pstrDate format:(NSString *)aFormat
{
    if (pstrDate.length == 0)
    {
        return nil;
    }

    NSDateFormatter *df1 = [[NSDateFormatter alloc] init];
    [df1 setDateFormat:aFormat];
    NSDate *dtPostDate = [df1 dateFromString:pstrDate];
    return dtPostDate;
}

效果图

（无）

备注

（无）