Unable to validate a date string in ISO 8601 date format

Question

In asp.net Date.Now generates a complete date string: e.g "2018-01-17T11:12:42.0544453+00:00"

I am unable to validate this date string with the following formats. Can anyone suggest a suitable validation format?

Dim formats() As String = {
  "yyyy-MM-dd",
  "yyyy-MM-ddTHH:mm:ss",
  "yyyy-MM-ddTHH:mm:ss.fff",
  "yyyy-mm-ddThh:mm:ss.ffffff",
  "yyyy-mm-ddThh:mm:ss.fffffffZ",
  "yyyy-mm-ddThh:mm:ss.nnnnnnn",
  "yyyy-mm-ddThh:mm:ss.nnnnnnnZ",
  "yyyy-mm-ddThh:mm:ss.nnnnnnn+|-hh:mm"
}
If Date.TryParseExact("2018-01-17T11:12:42.0544453+00:00", formats, CultureInfo.InvariantCulture, DateTimeStyles.None, dt) Then
  //Success
End If

Answer 1

I want to ensure the date is a valid ISO 8601 date format. This can be true even when time/fractions/timeszones are omitted.

You can use the "O"(Round-trip) format specifier

Dim time = "2018-01-17T11:12:42.0544453+00:00"
Dim validDate = Date.TryParseExact(time, "O", CultureInfo.InvariantCulture, DateTimeStyles.None, dt)

The "O" or "o" standard format specifier represents a custom date and time format string using a pattern that preserves time zone information and emits a result string that complies with ISO 8601. For DateTime values, this format specifier is designed to preserve date and time values along with the DateTime.Kind property in text. ...

Side-note: for me Date.Now.ToString doesn't return a string in this format. Maybe you have used:

Dim time = Date.UtcNow.ToString("o", System.Globalization.CultureInfo.InvariantCulture)