apply DayLightSavingTime to NSDate

Question

I get a NSDate from a UIDatePicker (timePicker) which is converted to the users time zone but it is one hour off because I'm in Summer Time.

So I tried to check if the User is in Summer Time if yes it should add the time to the NSDate/dateInUserTimezone.

How can I achieve this?

func convertTimeZone() ->NSDate {
        var date = timePicker.date
        print(date)
        var formatter = NSDateFormatter()

        let timeZone = NSTimeZone(abbreviation: userTimeZone())
        formatter.timeZone = timeZone
        formatter.dateFormat = "HH:mm:ss"

        var isDaylightSavingTime: Bool {
            return NSTimeZone.localTimeZone().daylightSavingTime
        }
        print(isDaylightSavingTime)

        var daylightSavingTimeOffset: NSTimeInterval {
            return NSTimeZone.localTimeZone().daylightSavingTimeOffset
        }

        let dateInUserTimezone = formatter.dateFromString(formatter.stringFromDate(date))

        return dateInUserTimezone!
    }

    func userTimeZone() -> String {
        return NSTimeZone.localTimeZone().abbreviation ?? ""
    }

Answer 1

NSDate is inherently in UTC (it has no timezone). Best to save/transfer your dates in UTC. Then, you can convert this UTC time stamp to any time zone of your preference. Instead of detecting whether the user is DST or not, try converting to your preferred time zone. Here's an example of how you would convert any date to local time zone.

var date = ...
var myTimeZone = NSTimeZone.localTimeZone()
var df = NSDateFormatter()
df.timeZone = myTimeZone
df.dateFormat = "yyyy.MM.dd G 'at' HH:mm:ss zzz"
df.stringFromDate(date)