Question

I m a iOS developer of the iWorld. I ve developed several iPhone/iPad apps before. I couldn t get correct time information on iPhone several times. I think that is due to localization.

For example, I have code to get the time-truncated today. (ex : "05-04-2012 00:00:00") But that code always return 8 hours ago to that I ve expected. (ex : "05-03-2012 16:00:00) The code that I ve worked are as following.

NSDate *today = [NSDate date];
NSCalendar *calender = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components = [calender components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit fromDate:today];
today = [calender dateFromComponents:components];
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"MM-dd-yyyy hh:mm:ss"];
NSString *todayString = [formatter stringFromDate:today];
NSLog(@"Today is %@", todayString);

I d like to hear from you to resolve this problem. Thanks for your time.

Answer 1

I ve found that code that calculates correct midnight time. Now I find that following code logs "Today is 05-07-2012 00:00:00" rather than "05-06-2012 16:00:00"

NSDate *today = [NSDate date];
NSCalendar *calender = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components = [calender components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit fromDate:today];
today = [calender dateFromComponents:components];

today = [today dateByAddingTimeInterval:[[NSTimeZone localTimeZone] secondsFromGMT]];

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"MM-dd-yyyy hh:mm:ss"];
NSString *todayString = [formatter stringFromDate:today];
NSLog(@"Today is %@", todayString);

Thanks for SO.

Answer 2

规定时间区到美国

    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    NSTimeZone *timeZone = [NSTimeZone timeZoneWithName:@"UTC"];
    [dateFormatter setTimeZone:timeZone];

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