public static bool CheckDate(string day, string month, string year)
{
const string monthPattern = @"(1[0-2]|0[1-9]|\d)";
const string yearPattern = @"(19|2[0-1])\d{2}$";
const string dayPattern = @"[0-9]";
return IsCorrectFieldData(month, monthPattern)
&& IsCorrectFieldData(year, yearPattern)
&& IsCorrectFieldData(day, dayPattern);
}