Regex in C# to get UTC date...

I recently needed to find a UTC date in a string of text, and I thought it might be handy to pull the various values from the dates that were found by getting the values from the returned Groups for each Match. Groups are identified in your regular expression string by surrounding sections with parentheses. The first Group of every match is the string value that the Match found. Every other group in the Match is identified by the parentheses going from left to right. So, if you have a regular expression that looks like this:

"((\d\d\d\d)-(\d\d)-(\d\d))T((\d\d):(\d\d):(\d\d))Z"

Imagine that someone used the above regular expression on the following string.

"This is a UTC date : 1999-12-31T23:59:59Z. Get ready to party!"

The very first group (after the matched date/time string) will be the entire date, because the first set of parentheses completely wraps the date portion of the string.

"1999-12-31"

The next group would be the year portion of the date, since the next set of parentheses completely wraps the year.

"1999"

That pattern is repeated for the rest of the regular expression string. If no parentheses (groupings) are specified, then there will only be the one group and it will contain the string that the regular expression matched. Here is an example of how to do this in code:

static void Main(string[] args)
{
    string input = "this\tis\ta test 2013-03-21T12:34:56Z\tand\tanother date\t2013-03-21T23:45:01Z";
    string regexString = @"((\d\d\d\d)-(\d\d)-(\d\d))T((\d\d):(\d\d):(\d\d))Z";
    TestRegex(input, regexString);
}

private static void TestRegex(string input, string regexString)
{
    int matchCount = 0;
    foreach (Match match in Regex.Matches(input, regexString))
    {                
        int groupCount = 0;
        foreach (Group group in match.Groups)
        {
            Console.WriteLine("Match {0}, Group {1} : {2}", 
                                matchCount, 
                                groupCount++, 
                                group.Value);    
        }
        matchCount++;
    }
}

Here is the output:

Match 0, Group 0 : 2013-03-21T12:34:56Z
Match 0, Group 1 : 2013-03-21
Match 0, Group 2 : 2013
Match 0, Group 3 : 03
Match 0, Group 4 : 21
Match 0, Group 5 : 12:34:56
Match 0, Group 6 : 12
Match 0, Group 7 : 34
Match 0, Group 8 : 56
Match 1, Group 0 : 2013-03-21T23:45:01Z
Match 1, Group 1 : 2013-03-21
Match 1, Group 2 : 2013
Match 1, Group 3 : 03
Match 1, Group 4 : 21
Match 1, Group 5 : 23:45:01
Match 1, Group 6 : 23
Match 1, Group 7 : 45
Match 1, Group 8 : 01