iOS 获取零点时间

 NSCalendar *calendar = [NSCalendar currentCalendar];
 NSDate *currentDate = [NSDate date];

 NSDateComponents *components = [calendar components:NSCalendarUnitYear|NSCalendarUnitMonth|NSCalendarUnitDay fromDate:currentDate];
 NSDate *zeroDate = [calendar dateFromComponents:components];

 NSDate* now = [NSDate date];

 NSCalendar *cal = [NSCalendar currentCalendar];

 unsigned int unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSCalendarUnitHour | NSMinuteCalendarUnit |NSSecondCalendarUnit;

 NSDateComponents*zerocompents = [calcomponents:unitFlagsfromDate:now];

 NSLog(@"%@",zerocompents);

 // 转化成0晨0点时间
 zerocompents.hour=0;
 zerocompents.minute=0;
 zerocompents.second=0;

 NSLog(@"%@",zerocompents);
 // NSdatecomponents转NSdate类型
 NSDate*newdate= [caldateFromComponents:zerocompents];
 // //时间转毫秒的时间戳格式(该时间已经是当天凌晨零点的时刻)
 NSTimeInterval zerointerval = [newdate timeIntervalSince1970]*1000;