using System.Text.RegularExpressions;
public static void Main()
string pattern = @"^([12]\d{3}-(0[1-9]|1[0-2])-(0[1-9]|[12]\d|3[01]))$";
Regex regex = new Regex(pattern);
Console.WriteLine(regex.Matches("1021-1-1").Count);
Console.WriteLine((regex.Matches("1021-11-02T")).Count);