Direct Translation:
* Saisissez le jour: This is the most literal translation, and it's a good general option.
More Idiomatic:
* Profitez du jour: This emphasizes enjoying the day.
* Ne laissez pas passer votre chance: This emphasizes not missing an opportunity.
* Prenez votre chance: This means "take your chance" and is a more active way of saying seize the day.
Literary:
* Carpe diem: This is the Latin phrase, which is often used in French as well.
The best translation will depend on the specific context and the message you want to communicate.