Converting date between timezones swift

Question

I have a date stored on my online server database which is in GMT. I load the date and convert it to the user's timezone using the following code :

 if let messagedate = oneitem["timestamp"] as? String {      let dateFormatter = NSDateFormatter()      dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"      let date = dateFormatter.dateFromString(messagedate)      let source_timezone = NSTimeZone(abbreviation: "GMT")      let local_timezone = NSTimeZone.systemTimeZone()      let source_EDT_offset = source_timezone?.secondsFromGMTForDate(date!)      let destination_EDT_offset = local_timezone.secondsFromGMTForDate(date!)      let time_interval : NSTimeInterval = Double(destination_EDT_offset - source_EDT_offset!)        let final_date = NSDate(timeInterval: time_interval, sinceDate: date!)      curr_item.date = final_date  } 

Now I need to convert the date back to GMT in order to communicate it to the server, however I'm not sure how to convert it back to GMT.

Answer 1

Couldn't you just use your data formatter again with a different time zone and convert it? Such as

dateFormatter.timeZone = NSTimeZone(abbreviation: "GMT") let gmtDate = dateFormatter.dateFromString(string: "your old date as string here")