[TestMethod]
    public void DateTimeConvertTest() {
      var ruTimeZone = TimeZoneInfo.FindSystemTimeZoneById( "Russian Standard Time" );
      var euTimeZone = TimeZoneInfo.FindSystemTimeZoneById( "Central Europe Standard Time" );

      DateTime ruDate, euDate;
      euDate = new DateTime( 2013, 02, 13, 9, 0, 0 );
      ruDate = TimeZoneInfo.ConvertTime( euDate, euTimeZone, ruTimeZone );
      Assert.AreEqual( new TimeSpan( 3, 0, 0 ), ruDate - euDate );
      euDate = new DateTime( 2017, 02, 13, 9, 0, 0 );
      ruDate = TimeZoneInfo.ConvertTime( euDate, euTimeZone, ruTimeZone );
      Assert.AreEqual( new TimeSpan( 2, 0, 0 ), ruDate - euDate );
      euDate = new DateTime( 2013, 06, 13, 9, 0, 0 );
      ruDate = TimeZoneInfo.ConvertTime( euDate, euTimeZone, ruTimeZone );
      Assert.AreEqual( new TimeSpan( 2, 0, 0 ), ruDate - euDate );
      euDate = new DateTime( 2017, 06, 13, 9, 0, 0 );
      ruDate = TimeZoneInfo.ConvertTime( euDate, euTimeZone, ruTimeZone );
      Assert.AreEqual( new TimeSpan( 1, 0, 0 ), ruDate - euDate );
    }