Regex for 12hr and 24hr time format

Question

I am using two regex for validating time in 12hr and 24hr format,but in some cases it is not working.Am i doing something wrong in these regex?It is not working

For validating 12 hr format like 10:00 AM/12:00 PM i have used regex

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

For validating 24 hr format like 23:00/12:00 i have used regex

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

Answer 1

I'm not sure why you have some of the 24 hr format in your first regex. The 12 hr format alone could be simplified to this:

new Regex(@"^(?:0?[0-9]|1[0-2]):[0-5][0-9] [ap]m$", RegexOptions.IgnoreCase);

And for the 24 hr format, you can simplify it to:

new Regex(@"^(?:[01][0-9]|2[0-3]):[0-5][0-9]$");

Or to combine both:

new Regex(@"^(?:(?:0?[0-9]|1[0-2]):[0-5][0-9] [ap]m|(?:[01][0-9]|2[0-3]):[0-5][0-9])$", RegexOptions.IgnoreCase);