Regular expression to validate valid time

I don't want to steal anyone's hard work but this is exactly what you're looking for, apparently.

using System.Text.RegularExpressions;

public bool IsValidTime(string thetime)
{
    Regex checktime =
        new Regex(@"^(20|21|22|23|[01]d|d)(([:][0-5]d){1,2})$");

    return checktime.IsMatch(thetime);
}

The regex ^(2[0-3]|[01]d)([:][0-5]d)$ should match 00:00 to 23:59. Don't know C# and hence can't give you the relevant code.

/RS

If you want to allow military and standard with the use of AM and PM (optional and insensitive), then you may want to give this a try.

^(?:(?:0?[1-9]|1[0-2]):[0-5][0-9]\s?(?:[AP][Mm]?|[ap][m]?)?|(?:00?|1[3-9]|2[0-3]):[0-5][0-9])$