.h文件

//
//  NSDate+XMGExtension.h
//  01-百思不得姐
//
//  Created by xiaomage on 15/7/27.
//  Copyright (c) 2015年 小码哥. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface NSDate (XMGExtension)
/**
 * 比较from和self的时间差值
 */
- (NSDateComponents *)deltaFrom:(NSDate *)from;

/**
 * 是否为今年
 */
- (BOOL)isThisYear;

/**
 * 是否为今天
 */
- (BOOL)isToday;

/**
 * 是否为昨天
 */
- (BOOL)isYesterday;
@end

.m文件

//
//  NSDate+XMGExtension.m
//  01-百思不得姐
//
//  Created by xiaomage on 15/7/27.
//  Copyright (c) 2015年 小码哥. All rights reserved.
//

#import "NSDate+XMGExtension.h"

@implementation NSDate (XMGExtension)
- (NSDateComponents *)deltaFrom:(NSDate *)from
{
    // 日历
    NSCalendar *calendar = [NSCalendar currentCalendar];
    
    // 比较时间
    NSCalendarUnit unit = NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond;
    
    return [calendar components:unit fromDate:from toDate:self options:0];
}

- (BOOL)isThisYear
{
    // 日历
    NSCalendar *calendar = [NSCalendar currentCalendar];
    
    NSInteger nowYear = [calendar component:NSCalendarUnitYear fromDate:[NSDate date]];
    NSInteger selfYear = [calendar component:NSCalendarUnitYear fromDate:self];
    
    return nowYear == selfYear;
}

//- (BOOL)isToday
//{
//    // 日历
//    NSCalendar *calendar = [NSCalendar currentCalendar];
//    
//    NSCalendarUnit unit = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;
//    
//    NSDateComponents *nowCmps = [calendar components:unit fromDate:[NSDate date]];
//    NSDateComponents *selfCmps = [calendar components:unit fromDate:self];
//    
//    return nowCmps.year == selfCmps.year
//    && nowCmps.month == selfCmps.month
//    && nowCmps.day == selfCmps.day;
//}

- (BOOL)isToday
{
    NSDateFormatter *fmt = [[NSDateFormatter alloc] init];
    fmt.dateFormat = @"yyyy-MM-dd";
    
    NSString *nowString = [fmt stringFromDate:[NSDate date]];
    NSString *selfString = [fmt stringFromDate:self];
    
    return [nowString isEqualToString:selfString];
}

- (BOOL)isYesterday
{
    // 2014-12-31 23:59:59 -> 2014-12-31
    // 2015-01-01 00:00:01 -> 2015-01-01
    
    // 日期格式化类
    NSDateFormatter *fmt = [[NSDateFormatter alloc] init];
    fmt.dateFormat = @"yyyy-MM-dd";
    
    NSDate *nowDate = [fmt dateFromString:[fmt stringFromDate:[NSDate date]]];
    NSDate *selfDate = [fmt dateFromString:[fmt stringFromDate:self]];
    
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDateComponents *cmps = [calendar components:NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear fromDate:selfDate toDate:nowDate options:0];
    
    return cmps.year == 0
    && cmps.month == 0
    && cmps.day == 1;
}

@end

说明：出自MJ