时间差计算（给定两时间，转换为时间差）

-(NSString *)getchaWithBegin:(NSString *)begin WithEnd:(NSString *)end

{

[email protected]"20150615184030";

end= @"20150615204130";

NSCalendar *cal = [NSCalendar currentCalendar];

NSInteger unitFlag = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSWeekdayCalendarUnit |  NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;

NSDateFormatter* df2 = [[NSDateFormatter alloc]init];

[df2 setDateFormat:@"yyyyMMddHHmmss"];//（格式自己定制）

NSDateComponents *d = [cal components:unitFlag fromDate:[df2 dateFromString:begin] toDate:[df2 dateFromString:end]options:0];

//    int sec = [d hour]*3600+[d minute]*60+[d second];

//    NSLog(@"second = %ld",[d hour]);

NSLog(@"%@",[NSString stringWithFormat:@"%ld小时%ld分",[d day]*24+[d hour],(long)[d minute]]);

return [NSString stringWithFormat:@"%ld小时%ld分",[d day]*24+[d hour],(long)[d minute]];

// 返回多少小时多少分钟

}