C#/Xamarin iOS - Converts a UTC DateTime to the device local Time Zone as System.DateTime. Also includes functions to convert iOS native date times to System.DateTime and back again.

gistfile1.cs

		/// <summary>
		/// Converts a UTC datestamp to the local timezone
		/// </summary>
		/// <returns>The UTC to local time zone.</returns>
		/// <param name="dateTimeUtc">Date time UTC.</param>
		public DateTime ConvertUTCToLocalTimeZone (DateTime dateTimeUtc)
		{
			NSTimeZone sourceTimeZone = new NSTimeZone ("UTC");
			NSTimeZone destinationTimeZone = NSTimeZone.LocalTimeZone;
			NSDate sourceDate = DateTimeToNativeDate (dateTimeUtc);

			int sourceGMTOffset = sourceTimeZone.SecondsFromGMT (sourceDate);
			int destinationGMTOffset = destinationTimeZone.SecondsFromGMT (sourceDate);
			int interval = destinationGMTOffset - sourceGMTOffset;

			var destinationDate = sourceDate.AddSeconds (interval);
			var dateTime = NativeDateToDateTime (destinationDate);
			return dateTime;
		}

		/// <summary>
		/// Converts a System.DateTime to an NSDate
		/// </summary>
		/// <returns>The time to native date.</returns>
		/// <param name="date">Date.</param>
		public static NSDate DateTimeToNativeDate(DateTime date)
		{
			DateTime reference = TimeZone.CurrentTimeZone.ToLocalTime(
				new DateTime(2001, 1, 1, 0, 0, 0) );
			return NSDate.FromTimeIntervalSinceReferenceDate(
				(date - reference).TotalSeconds);
		}

		/// <summary>
		/// Converts a NSDate to System.DateTime
		/// </summary>
		/// <returns>The date to date time.</returns>
		/// <param name="date">Date.</param>
		public static DateTime NativeDateToDateTime(NSDate date)
		{
			DateTime reference = TimeZone.CurrentTimeZone.ToLocalTime( 
				new DateTime(2001, 1, 1, 0, 0, 0) );
			return reference.AddSeconds(date.SecondsSinceReferenceDate);
		}