Trois heures ou Treize heures?

Question

Isn't it odd to say she has French à trois heures (which is in the middle of the night?)  Would it not be be more reasonable to say à très heures de l'après-midi or à treize heures?

Accepted Answer

Susan, it is very common in French to use the 12 hour clock. 
Just as in English, when the context is clear, du matin, de l’après-midi or du soir are regularly dropped in everyday speech.
As you note, it would be strange indeed to have French at ‘3 in the morning’, but in that case, you would definitely need to say ‘…. à trois heures du matin’ ! Otherwise it is not essential to say ‘… à quinze heures ‘, or ‘…à trois heures de l’après-midi’, although either would be fine.
The 24 hour clock is used in French more than in everyday English in my experience, but still less than the 12 hour clock. Many use a combination of the 2 systems when clarity is needed.
Amongst our French family and friends, only the ex-train driver always expresses time by the 24 hour clock. Old habits ….

Answer

Hi Susan,
Just to add to Maarten's excellent answer, we could have said -
à quinze heures (3pm)
but we didn't to reflect what happens in real life in France.
It would be obvious in the context that we are talking about 'trois heures (de l'après-midi).
Bonne Continuation !