C# Regex Time Validation With Regular Expression

In order to check whether an input is a valid time format or not,
regular expressions can be used to validate the input value.

The sample function below show how to check if the input
is valid time in XX:XX, code is in C#.

This regular expression checks the input for 00:00 to 23:59 is a valid time format.

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);
} 

Time regular expression used to control time is ^(20|21|22|23|[01]\d|\d)(([:][0-5]\d){1,2})$

Is valid time validation with regular expression in C#.