Question

I have a NSString (date) retrieved from my MySQL database which is in GMT +000 (London) and its format is like this: 12/05/2011 5:21:29 PM.

I would like to know how I could convert it to the user’s time zone so that if the user was in china for example, it would be that date in the chinese time zone.

Answer 1

Use setTimeZone: on your input NSDateFormatter. (Internally, NSDates are time zone agnostic.)

E.g.:

// The default time zone for a formatter is the time zone of the user's locale
NSDateFormatter *localFormatter = [[NSDateFormatter alloc] init];
[localFormatter setDateStyle:NSDateFormatterShortStyle];
[localFormatter setTimeStyle:NSDateFormatterMediumStyle];

NSDateFormatter *gmtFormatter = [[NSDateFormatter alloc] init];
[gmtFormatter setDateFormat:@"MM/dd/yyyy h:mm:ss a"];
[gmtFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];

NSDate *date = [gmtFormatter dateFromString:gmtDateString];
NSString *locallyFormattedDate = [localFormatter stringFromDate:date];

[localFormatter release];
[gmtFormatter release];

Although…I don’t think this takes DST into account if the DST setting during the specified time is different than the current setting.