Regular expression for time validation

[Pallavi]

Hi All,

Our Application displays the below text. We need to validate this.
In the below text, the date and time is US date and time, as the application displays the server date and time and our server is residing in US.
Here, I need not validate the exact time. Need to validate just the time pattern. So can this be done using regular expression?
If Yes, could you please let me know how to validate the below text.

Text displayed in application:
UBIL MOD MODERATE CORRECTED ON 03/07/2012 AT 2258: PREVIOUSLY REPORTED AS SML

Thanks and Regards,
Pallavi