AS3:

var testDate:Date = new Date(2010, 05, 27, 5, 55, 32, 10);
trace(testDate.getTime());

C#:

DateTime testDate = new DateTime(2010, 05, 27, 5, 55, 32, 10, DateTimeKind.Utc);  System.TimeSpan span = testDate - (new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc));

Console.WriteLine(span.TotalMilliseconds);