Question

I’m trying to find the appropriate format string to parse (exact) the following types of dates:

• 1-01-01T00:00:00+00:00 – 1 January of 0001
• 2011-12-14T15:53:40+00:00 – 14 December of 2011

So the year length seems to be variable (1-4 characters).

The format sting I currently use to parse exact is:
c_DateTimeFormatString = "yyyy-MM-ddTHH':'mm':'sszzz"

Obviously this only matches the second string. The first one poped up today. Now we have to match that as well.

Is there a format string to achieve this?

UPDATE #1
I added the actual dates in clear text after the input date strings.

UPDATE #2
Parse exact has an overload that allows for multiple format strings to be passed in. This seems to be the right way.

So the first try was to use:

DateTime.ParseExact("1-01-01T00:00:00+00:00 ", new[] { "yyyy-MM-ddTHH':'mm':'sszzz", "yyy-MM-ddTHH':'mm':'sszzz", "yy-MM-ddTHH':'mm':'sszzz", "y-MM-ddTHH':'mm':'sszzz" }, CultureInfo.CreateSpecificCulture("en-US"), DateTimeStyles.AssumeLocal)

But sadly this does ont give the correct result, the first date string is parsed as:
01.01.2001
rather than
01.01.0001

So the question now is what is the correct parsing string to parse year one which is represented with only one digit?

Answer 1

Updated based on comment:

string y = "yyyy-MM-ddTHH':'mm':'sszzz";

string testDate = "1-01-05T00:00:00+00:00".PadLeft(25, '0');
Console.WriteLine(DateTime.ParseExact(testDate, y, CultureInfo.InvariantCulture));
testDate = "2011-12-14T15:53:40+00:00".PadLeft(25, '0');
Console.WriteLine(DateTime.ParseExact(testDate, y, CultureInfo.InvariantCulture));

The output is:

1/5/0001 00:00:00
12/14/2011 15:53:40