获取当天 0 点得时间戳 也可以是 某一个点或者时刻的时间戳

        NSDate *date = [NSDate date];

        NSTimeZone *gmt = [NSTimeZone timeZoneWithAbbreviation:@"GMT"];

        NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier: NSGregorianCalendar];

        [gregorian setTimeZone:gmt];

        NSDateComponents *components = [gregorian components: NSUIntegerMax fromDate: date];

        [components setHour: 0];

        [components setMinute:0];

        [components setSecond: 0];

        NSDate *newDate = [gregorian dateFromComponents: components];

        NSLog(@"zero time :%@",newDate);

        NSString *timeSp = [NSString stringWithFormat:@"%ld", (long)[newDate timeIntervalSince1970]];

        NSLog(@"zerotime str :%@",timeSp);

 时间戳转时间 

-(NSString *)setTimeStampStrToDate:(NSString *)timeStamp

{

    NSDateFormatter *formatterSet = [[NSDateFormatter alloc] init];

    [formatterSet setDateStyle:NSDateFormatterMediumStyle];

    [formatterSet setTimeStyle:NSDateFormatterShortStyle];

    [formatterSet setDateFormat:@"YYYY-MM-dd HH:mm"];

    NSDate *titleDate = [NSDate dateWithTimeIntervalSince1970:[timeStamp intValue]];

    return  [formatterSet stringFromDate:titleDate];

} 

 当前时间转时间戳 

NSString *timeSp = [NSString stringWithFormat:@"%ld", (long)[[NSDate date] timeIntervalSince1970]];