@maxdancona,
The days of the week are named after the seven classical planets or the gods associated with them.
Monday Moon
Tuesday Mars (Mardi)
Wednesday Mercury (Mercredi)
Thursday Jupiter (Jeudi)
Friday Venus (Ventredi)
Saturday Saturn
Sunday Sun
I’ve given you the French to help out with some weekdays.
I know the Sun and Moon aren’t planets but they are as far as the ancients understood the term.
7 planets, 7 days of the week.