Formatting Date from server time to local time using NSTimeZone and Dateformatter - nsdate

Question

I am receiving a date/time as a NSString from my server where I am converting that time into a NSDate to the users local time using NSTimeZone. After which I try to reformat this NSDate into a better more readable NSString using the new NSDateFormatter format, however when I try to apply this new format it reverts the resulting dateString back to the original Server time.
I would like to know what I am doing wrong, I would like to show the converted time in the new format.
this is the code I am using
// set date format
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
dateFormatter.dateFormat = #"yyyy-MM-dd HH:mm:ss";
// change time to systemTimeZone
NSTimeZone *timeZone = [NSTimeZone systemTimeZone];
[dateFormatter setTimeZone:timeZone];
NSDate *localTime = [dateFormatter dateFromString:[singleInstanceActivationHistoryDictionay objectForKey:#"ActivationTime"]];
// reformat converted Time to readable format
NSDateFormatter *dateFormat1 = [[NSDateFormatter alloc] init];
[dateFormat1 setDateFormat:#"dd/MM/yy - hh:mm a"];
NSString *dateWithNewFormat = [dateFormat1 stringFromDate:localTime];
NSLog(#"TimeZone - %#", timeZone);
NSLog(#"UTC ServerTime - %#", [singleInstanceActivationHistoryDictionay objectForKey:#"ActivationTime"]);
NSLog(#"UTC to deviceTimeZone - %#", localTime);
NSLog(#"NewFormat - %#", dateWithNewFormat);
This is an example of my output
TimeZone - Pacific/Auckland (NZST) offset 43200
UTC ServerTime - 2013-08-22 01:45:59
UTC to deviceTimeZone - 2013-08-21 13:45:59 +0000
NewFormat - 22/08/13 - 01:45 AM
any help would be greatly appreciated

Answer 1

The NSDateFormatter that reads the date must be set to the timezone that the date you are parsing is in, in your case, it is UTC. The date formatter will then be able to produce an NSDate object (which represents a specific moment in time regardless of timezones). You can then give that NSDate object to another NSDateFormatter that is configured to format dates in a specific time zone.
// set date format
NSDateFormatter *dateParser = [[NSDateFormatter alloc] init];
dateParser.dateFormat = #"yyyy-MM-dd HH:mm:ss";
dateParser.timeZone = [NSTimeZone timeZoneWithName:#"UTC"];
NSDate *specificMomentInTime = [dateParser dateFromString:[singleInstanceActivationHistoryDictionay objectForKey:#"ActivationTime"]];
// reformat converted Time to readable format
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
dateFormatter.dateFormat = #"dd/MM/yy - hh:mm a";
dateFormatter.timeZone = [NSTimeZone defaultTimeZone];
NSString *dateWithNewFormat = [dateFormatter stringFromDate:specificMomentInTime];
NSLog(#"UTC ServerTime - %#", specificMomentInTime);
NSLog(#"NewFormat - %#", dateWithNewFormat);