public void SpecifyTimeZoneDaylightTest()
        {
            var dt = new DateTime(1990, 2, 1, 12, 0, 0, DateTimeKind.Local); // just a test
            var tz = TimeZoneService.FindSystemTimeZoneById("Central Standard Time");

            var result = TimeZoneService.SpecifyTimeZone(dt, tz);

            result.Hour.Should()
            .Be(12);       // same
            result.Offset.Should()
            .Be(TimeSpan.FromHours(-6));
        }