Talking clock in a different language

I've got my Mac speaking me the time every hour, but I'm currently trying to learn French so I thought it would be a good idea to make it speak the time in French.

However, rather than saying "Il est 11 heures." she says "It's 11 hours." (in a lovely French accent).

Is it possible to make her actually speak French?

How did you set up the system to say the time?

I set it up as follows: System Preferences --> Dictation & Speech --> Text to Speech --> Customize --> Add a French voice. It took some time to download.

And then on the command line:

$ export LANG=fr_FR
$ say `date`

This works for me.

What might work in the GUI is to set the date format to French:

System Preferences --> Language & Region --> Advanced --> Format Language - French

As you can see in the screenshots below, this changes the date and format only, not the entire language of the system.