Xamarin 'iOS Foundation NSDate to C# DateTime conversion' and vice versa not accounting for DayLight saving

Question

I need to convert Cocoa NSDate to C# DateTime and vice versa.

I am using the following method to achieve this:

 public static DateTime NSDateToDateTime (Foundation.NSDate date)
 {
    DateTime reference = TimeZone.CurrentTimeZone.ToLocalTime (
        new DateTime (2001, 1, 1, 0, 0, 0));
   return reference.AddSeconds (date.SecondsSinceReferenceDate);
 }

 public static Foundation.NSDate DateTimeToNSDate (DateTime date)
 {
    DateTime reference = TimeZone.CurrentTimeZone.ToLocalTime (
        new DateTime (2001, 1, 1, 0, 0, 0));
    return Foundation.NSDate.FromTimeIntervalSinceReferenceDate (
        (date - reference).TotalSeconds);
 }

But it turns out, this way it is not accounting for Daylight Saving.

Eg. DateTime object in which the time was 5AM in DST returns NSDate with time 6AM.

Answer 1

I'm pretty sure this is an outdated approach. You can cast a NSDate directly to a DateTime now.

 Foundation.NSDate nsDate = // someValue
 DateTime dateTime = (DateTime)nsDate;

Answer 2

Based on inputs from: https://forums.xamarin.com/discussion/27184/convert-nsdate-to-datetime


Local Time changes during Daylight Saving. Hence, always convert to UTC to do the calculations, then convert to Local time if needed.

     public static DateTime NSDateToDateTime (Foundation.NSDate date)
     {
        DateTime reference = new DateTime(2001, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
        var utcDateTime = reference.AddSeconds(date.SecondsSinceReferenceDate);
        return utcDateTime.ToLocalTime();
     }

     public static Foundation.NSDate DateTimeToNSDate (DateTime date)
     {
        DateTime reference = new DateTime(2001, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
        var utcDateTime = date.ToUniversalTime();
        return Foundation.NSDate.FromTimeIntervalSinceReferenceDate((utcDateTime - reference).TotalSeconds);
     }