Formal:
* Dimanche après-midi: This is the most literal and formal translation.
* L'après-midi du dimanche: This is another formal option that emphasizes the "afternoon of Sunday."
Informal:
* Dimanche après-midi: This is also used informally, but it's less common than the next option.
* L'après-midi de dimanche: This is a more natural way to say it in everyday conversation.
You could also use a more specific time, such as:
* Dimanche après-midi, vers 14h: Sunday afternoon, around 2 pm.
* Dimanche après-midi, vers 16h: Sunday afternoon, around 4 pm.
Ultimately, the best way to say "Sunday afternoon" in French depends on the specific situation.