public void FromSwatchInternetTime()
        {
            TimeZoneInfo utc     = TimeZoneInfo.FindSystemTimeZoneById("UTC");
            TimeZoneInfo romance = TimeZoneInfo.FindSystemTimeZoneById("Romance Standard Time");

            var r1 = EssentialsTime.FromSwatchInternetTime(2020, 8, 17, 315, utc);
            var r2 = EssentialsTime.FromSwatchInternetTime(2020, 8, 17, 315, romance);

            var r3 = EssentialsTime.FromSwatchInternetTime(new EssentialsDate(2020, 8, 17), 315, utc);
            var r4 = EssentialsTime.FromSwatchInternetTime(new EssentialsDate(2020, 8, 17), 315, romance);

            var r5 = EssentialsTime.FromSwatchInternetTime(2020, 11, 14, 619, utc);
            var r6 = EssentialsTime.FromSwatchInternetTime(2020, 11, 14, 619, romance);

            var r7 = EssentialsTime.FromSwatchInternetTime(new EssentialsDate(2020, 11, 14), 619, utc);
            var r8 = EssentialsTime.FromSwatchInternetTime(new EssentialsDate(2020, 11, 14), 619, romance);

            Assert.AreEqual("2020-08-17T06:33:36.000Z", r1.Iso8601, "#1");
            Assert.AreEqual("2020-08-17T08:33:36.000+02:00", r2.Iso8601, "#2");

            Assert.AreEqual("2020-08-17T06:33:36.000Z", r3.Iso8601, "#1");
            Assert.AreEqual("2020-08-17T08:33:36.000+02:00", r4.Iso8601, "#2");

            Assert.AreEqual("2020-11-14T13:51:21.600Z", r5.Iso8601, "#5");
            Assert.AreEqual("2020-11-14T14:51:21.600+01:00", r6.Iso8601, "#6");

            Assert.AreEqual("2020-11-14T13:51:21.600Z", r7.Iso8601, "#7");
            Assert.AreEqual("2020-11-14T14:51:21.600+01:00", r8.Iso8601, "#8");
        }