Checking for US/UK time format


I am trying to check for US/UK time format with regex:

It works when tested on regex101: regex101: build, test, and debug regex
But for some reason it doesn’t seem to work at Xbench.
How to make it work in Xbench?

Thanks in advance!

For more information on regular expressions syntax used in Xbench, consult Regular Expressions and Microsoft Word Wildcards :: ApSIC Xbench Documentation.