Regular expression to validate valid time

Question

I need a regular expression to validate time.

Valid values would be from 0:00 to 23:59.

When the time is less than 10:00 it should also support one character numbers.

These are valid values:

• 9:00
• 09:00

Answer 1

Try this regular expression:

^(?:[01]?[0-9]|2[0-3]):[0-5][0-9]$

Or to be more distinct:

^(?:0?[0-9]|1[0-9]|2[0-3]):[0-5][0-9]$

Answer 2

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);
}