1、基本时间日历

// 1、获取当前时间  
    NSDate *now = [NSDate date];  
    NSDateFormatter *nowFormate = [[NSDateFormatter alloc] init];  
    nowFormate.dateFormat = @"yyyy-MM-dd HH:mm:ss";  
    NSString *nowTime = [nowFormate stringFromDate:now];  
    NSLog(@"nowTime = %@",nowTime);  
// 2、拿现在的时间和过去时间或者将来时间对比，计算出相差多少天，多少年，多少秒等等；  
    NSDate *beforTime = [nowFormate dateFromString:@"2014-06-14 19:25:00"];  
    NSCalendar *calender = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];  
    //世纪  
    NSInteger era  = kCFCalendarUnitEra;  
    //年  
    NSInteger year = kCFCalendarUnitYear;  
    //月  
    NSInteger month = kCFCalendarUnitMonth;  
    //小时  
    NSInteger hour = kCFCalendarUnitHour;  
    //分钟  
    NSInteger minute = kCFCalendarUnitMinute;  
    //秒  
    NSInteger second = kCFCalendarUnitSecond;  
      
    NSDateComponents *compsEra = [calender components:era fromDate:beforTime toDate:now options:0];  
    NSDateComponents *compsYear = [calender components:year fromDate:beforTime toDate:now options:0];  
    NSDateComponents *compsMonth = [calender components:month fromDate:beforTime toDate:now options:0];  
    NSDateComponents *compsHour = [calender components:hour fromDate:beforTime toDate:now options:0];  
    NSDateComponents *compsMinute = [calender components:minute fromDate:beforTime toDate:now options:0];  
    NSDateComponents *compsSecond = [calender components:second fromDate:beforTime toDate:now options:0];  
      
    NSLog(@"相差世纪个数 = %ld",[compsEra era]);  
    NSLog(@"相差年个数 = %ld",[compsYear year]);  
    NSLog(@"相差月个数 = %ld",[compsMonth month]);  
    NSLog(@"相差小时个数 = %ld",[compsHour hour]);  
    NSLog(@"相差分钟个数 = %ld",[compsMinute minute]);  
    NSLog(@"相差秒个数 = %ld",[compsSecond second]);  
      
    // 3、获取时间戳（相对于1970年）  
    CGFloat timestamp = now.timeIntervalSince1970;  
    NSLog(@"距离1970年有多少秒 = %f",timestamp);  
      
    // 4、计算距离现在有多少秒  
    CGFloat sinceNow = beforTime.timeIntervalSinceNow;  
    NSLog(@"距离现在有多少秒 = %f",fabs(sinceNow)); 

2、获取当前系统时间的时间戳

+(NSInteger)getNowTimestamp{
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateStyle:NSDateFormatterMediumStyle];
    [formatter setTimeStyle:NSDateFormatterShortStyle];
    [formatter setDateFormat:@"YYYY-MM-dd HH:mm:ss"]; // ----------设置你想要的格式,hh与HH的区别:分别表示12小时制,24小时制
    //设置时区,这个对于时间的处理有时很重要
    NSTimeZone* timeZone = [NSTimeZone timeZoneWithName:@"Asia/Beijing"];
    [formatter setTimeZone:timeZone];
    NSDate *datenow = [NSDate date];//现在时间
    NSLog(@"设备当前的时间:%@",[formatter stringFromDate:datenow]);
    //时间转时间戳的方法:
    NSInteger timeSp = [[NSNumber numberWithDouble:[datenow timeIntervalSince1970]] integerValue];
    NSLog(@"设备当前的时间戳:%ld",(long)timeSp); //时间戳的值
    return timeSp;
}

3、将某个时间转化成时间戳

+(NSInteger)timeSwitchTimestamp:(NSString *)formatTime andFormatter:(NSString *)format{
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateStyle:NSDateFormatterMediumStyle];
    [formatter setTimeStyle:NSDateFormatterShortStyle];
    [formatter setDateFormat:format]; //(@"YYYY-MM-dd hh:mm:ss") ----------设置你想要的格式,hh与HH的区别:分别表示12小时制,24小时制
    NSTimeZone* timeZone = [NSTimeZone timeZoneWithName:@"Asia/Beijing"];
    [formatter setTimeZone:timeZone];
    NSDate* date = [formatter dateFromString:formatTime]; //------------将字符串按formatter转成nsdate
    //时间转时间戳的方法:
    NSInteger timeSp = [[NSNumber numberWithDouble:[date timeIntervalSince1970]] integerValue];
    NSLog(@"将某个时间转化成 时间戳&&&&&&&timeSp:%ld",(long)timeSp); //时间戳的值
    return timeSp;
}

4、将某个时间戳转化成 时间

+(NSString *)timestampSwitchTime:(NSInteger)timestamp andFormatter:(NSString *)format{
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateStyle:NSDateFormatterMediumStyle];
    [formatter setTimeStyle:NSDateFormatterShortStyle];
    [formatter setDateFormat:format]; // （@"YYYY-MM-dd hh:mm:ss"）----------设置你想要的格式,hh与HH的区别:分别表示12小时制,24小时制
    NSTimeZone *timeZone = [NSTimeZone timeZoneWithName:@"Asia/Beijing"];
    [formatter setTimeZone:timeZone];
    NSDate *confromTimesp = [NSDate dateWithTimeIntervalSince1970:timestamp];
    NSLog(@"1296035591  = %@",confromTimesp);
    NSString *confromTimespStr = [formatter stringFromDate:confromTimesp];
    //NSLog(@"&&&&&&&confromTimespStr = : %@",confromTimespStr);
    return confromTimespStr;
}

5、获取当前时间字符串

- (NSString *)currentTimeStr {
    NSDateFormatter* dateFormat = [[NSDateFormatter alloc] init];
    [dateFormat setDateFormat:@"yyyy-MM-dd HH:mm"];
    NSString *currentDateStr = [dateFormat stringFromDate:[NSDate date]];
    return  currentDateStr;
}

6、简单将时间字符串转换为NSDate

- (NSDate *)dateFromString:(NSString *)dateString {
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat: @"yyyy-MM-dd HH:mm"];
    NSDate *destDate= [dateFormatter dateFromString:dateString];
    return destDate;
}

7、获取明天、下周、下个月时间字符串

typedef NS_ENUM(NSUInteger, EndTimeType) {
    EndTimeTypeDay,
    EndTimeTypeWeek,
    EndTimeTypeMonth,
};
- (NSString *)currentCycleEndTimeStrWithType:(EndTimeType)type withCurrentDate:(NSString *)currentDateStr {
    NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
    NSDateComponents *components = [gregorian components:NSCalendarUnitWeekday | NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay fromDate:[self cycleDateFromString:currentDateStr]];
    switch (type) {
        case EndTimeTypeDay:
            [components setDay:([components day]+1)];
            break;
        case EndTimeTypeWeek:
            [components setDay:([components day]+7)];
            break;
        case EndTimeTypeMonth:
            [components setMonth:([components month]+1)];
            break;
        default:
            break;
    }
    
    NSDate *beginningOfWeek = [gregorian dateFromComponents:components];
    NSDateFormatter *dateday = [[NSDateFormatter alloc] init];
    [dateday setDateFormat:@"yyy-MM-dd"];
    return [dateday stringFromDate:beginningOfWeek];
}

8、对比两个时间的先后关系

- (int)compareOneDay:(NSString *)oneDay withAnotherDay:(NSString *)anotherDay format:(NSString *)format {
    NSDateFormatter* dateFormat = [[NSDateFormatter alloc] init];
    [dateFormat setDateFormat:format];
    NSDate *dateA = [dateFormat dateFromString:oneDay];
    NSDate *dateB = [dateFormat dateFromString:anotherDay];
    NSComparisonResult result = [dateA compare:dateB];
    if (result == NSOrderedDescending) {
            //NSLog(@"oneDay比 anotherDay时间晚");
        return 1;
    }
    else if (result == NSOrderedAscending){
            //NSLog(@"oneDay比 anotherDay时间早");
        return -1;
    }
        //NSLog(@"两者时间是同一个时间");
    return 0;
}