Convert utc date into 12 hours local date? - ios

Question

My date and time is 20-Nov-2019 21:09 Which is in UTC 24 hours format. now I want to convert it into local time in 12 hours formate. 30-Nov-2019 08:00 AM like this.
My code is :
// create dateFormatter with UTC time format
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"dd-MMM-yyyy HH:mm"];
[dateFormatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"UTC"]];
// change to a readable time format and change to local time zone
[dateFormatter setDateFormat:#"dd-MMM-yyyy HH:mm a"];
[dateFormatter setTimeZone:[NSTimeZone localTimeZone]];
NSString *timestamp = [dateFormatter stringFromDate:date];
My code when i send my local time 12 formate into 24 hours UTC
-(NSString *)getUTCFormateDate:(NSDate *)localDate
{
// NSLog(#"%#", localDate);
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
NSTimeZone *timeZone = [NSTimeZone timeZoneWithName:#"UTC"];
[dateFormatter setTimeZone:timeZone];
[dateFormatter setDateFormat:#"dd-MMM-yyyy HH:mm"];
NSLocale *twelveHourLocale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US_POSIX"];
dateFormatter.locale = twelveHourLocale;
NSTimeInterval timeZoneoffset = [[NSTimeZone defaultTimeZone] secondsFromGMT];
NSTimeInterval utcTimeInterval = [localDate timeIntervalSinceReferenceDate] - timeZoneoffset;
NSDate *utcCurrentDate = [NSDate dateWithTimeIntervalSinceReferenceDate:utcTimeInterval];
NSString *dateString = [dateFormatter stringFromDate:utcCurrentDate];
// NSLog(#"dateString %#", dateString);
return dateString;
}
-(NSDate *)getUTCDate:(NSString *)currentDate{
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:#"dd-MMM-yyyy HH:mm"];
NSDate *date1 = [dateFormat dateFromString:currentDate];
if (date1 == nil){
[dateFormat setDateFormat:#"dd-MMM-yyyy hh:mm a"];
date1 = [dateFormat dateFromString:currentDate];
}
return date1;
}

Answer 1

I think you are doing too much. The format "hh" is the hour in 12-hour format, HH is 24-hour format. You should not have to set the locale for that (though setting to en_US_POSIX does avoid the user's 24-hour preference in the [NSLocale currentLocale] instance which can override that on iOS).
NSDate is an absolute instance in time. You need to apply a calendar and time zone with an NSDateFormatter to get numeric year/month/day etc. values out of it, but you don't need to adjust the offset to the reference date (that is changing the actual date, not just reformatting it in a different time zone).
NSString *utcString = #"20-Nov-2019 21:09";
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
formatter.timeZone = [NSTimeZone timeZoneWithName:#"UTC"];
formatter.locale = [NSLocale localeWithLocaleIdentifier:#"en_US_POSIX"];
formatter.dateFormat = #"dd-MMM-yyyy HH:mm";
NSDate *date = [formatter dateFromString:utcString];
formatter.timeZone = [NSTimeZone localTimeZone]; // GMT-5 for me
formatter.dateFormat = #"dd-MMM-yyyy hh:mm a";
NSLog(#"date: %#", [formatter stringFromDate:date]);
// date: 20-Nov-2019 04:09 PM