Timezone parsing issues

[bbrauns]

Hi! Thank you for providing this awesome implementation!

There seems to be a datetime related issue if I run for example the unit test EncodeDecode_WrongPublicKey which throws the error

System.FormatException: The UTC representation of the date '0001-01-01' falls outside the year range 1-9999.
...

Explicitly adding datetime values for SampleTakenDate and VaccinationDate in CreateCWTTestData() seems to fix that:

 var d = new DateTime(DateTime.UtcNow.Year, DateTime.UtcNow.Month, DateTime.UtcNow.Day, DateTime.UtcNow.Hour, DateTime.UtcNow.Minute, DateTime.UtcNow.Second, DateTimeKind.Unspecified);
            var o = new DateTimeOffset(d, TimeSpan.FromHours(0));
            var tests = new List<TestEntry>
            {
                new()
                {
                    CountryOfTest = "IS",
                    NAATTestName = "PCR Covid-19",
                    SampleTakenDate = o
                }
            };

            var d1 = new DateTime(DateTime.UtcNow.Year, DateTime.UtcNow.Month, DateTime.UtcNow.Day, 0,0,0, DateTimeKind.Unspecified);
            var o1 = new DateTimeOffset(d1, TimeSpan.FromHours(0));
            var vacs = new List<VaccinationEntry>
            {
                new()
                {
                    Issuer = "Test Issuer",
                    VaccinationDate = o1
                }
            };

But afterwards the JToken.DeepEquals fails because of differences regarding timezones of the property VaccinationDate. See the following json serializations:

cwtToTest.DGCv1:

{
    "DateOfBirthString": "2000-01-01",
    "DateOfBirth": "2000-01-01T00:00:00",
    "Name": {
        "SurnameName": "Testson",
        "SurameTransliterated": null,
        "GivenName": "Test",
        "GivenNameTraslitaerated": null
    },
    "Recovery": null,
    "Test": [{
            "CertificateIdentifier": null,
            "CountryOfTest": "IS",
            "Issuer": null,
            "RATTestDeviceIdentifier": null,
            "NAATTestName": "PCR Covid-19",
            "SampleTakenDate": "2021-06-24T07:35:46+00:00",
            "TestingCenter": null,
            "Disease": null,
            "TestResult": null,
            "TestType": null
        }
    ],
    "Vaccination": [{
            "CertificateIdentifier": null,
            "CountryOfVaccination": null,
            "DoseNumber": 0,
            "VaccinationDate": "2021-06-24T00:00:00+00:00",
            "Issuer": "Test Issuer",
            "Manufacturer": null,
            "MedicalProduct": null,
            "TotalDoses": 0,
            "Disease": null,
            "Vaccine": null
        }
    ],
    "Version": null
}

cwt.DGCv1:

{
    "DateOfBirthString": "2000-01-01",
    "DateOfBirth": "2000-01-01T00:00:00",
    "Name": {
        "SurnameName": "Testson",
        "SurameTransliterated": null,
        "GivenName": "Test",
        "GivenNameTraslitaerated": null
    },
    "Recovery": null,
    "Test": [{
            "CertificateIdentifier": null,
            "CountryOfTest": "IS",
            "Issuer": null,
            "RATTestDeviceIdentifier": null,
            "NAATTestName": "PCR Covid-19",
            "SampleTakenDate": "2021-06-24T07:35:46+00:00",
            "TestingCenter": null,
            "Disease": null,
            "TestResult": null,
            "TestType": null
        }
    ],
    "Vaccination": [{
            "CertificateIdentifier": null,
            "CountryOfVaccination": null,
            "DoseNumber": 0,
            "VaccinationDate": "2021-06-24T00:00:00+02:00",
            "Issuer": "Test Issuer",
            "Manufacturer": null,
            "MedicalProduct": null,
            "TotalDoses": 0,
            "Disease": null,
            "Vaccine": null
        }
    ],
    "Version": null
}

Or is there something I am missing which I have to configure accordingly? My PCs timezone: UTC +2 CEST Central European Summer Time Berlin