"Passez une bonne journée."
Here's a breakdown:
* Passez: This is the formal "you" form of the verb "passer" (to spend, to pass).
* une: This is the feminine singular definite article meaning "a".
* bonne: This is the feminine form of the adjective "bon" (good).
* journée: This means "day".
You can also use "bonne journée" by itself, which is a more casual way to say it.
"Bonne journée!"
Here are some other ways to say "have a good day" in French, depending on the context:
* "A bientôt!" (See you soon!)
* "Profitez de votre journée!" (Enjoy your day!)
* "Je vous souhaite une bonne journée!" (I wish you a good day!)