Hello, I moved your thread to the Samsung Galaxy S3 section where the members here can give you assistance to the clock app for your device.
Have you gone into it's settings and see if you can change it like that?

 

What about when you use Navigation? Is it in French or English?

I messed around with these settings, but I couldn't get my briefing to speak in French. You might double them to be sure they are set to English.

Settings / Language and input / Text-to-speech output / Google Text-to-speech Engine (Settings -Gear) / Language / English (United States)

Are you in the province of Quebec? Maybe it's a location service causing this, although there are no options under settings for language via location.

Last resort, you could try a factory reset (Settings / Back up and reset / Factory data reset). Of course it would reset your phone back to the state when you first unboxed it, so backup first.

 

Thanks for your question, i have same problem