À noter

La semaine - feminine, but the days are masculine.
French days of the week are not capitalised.
les jours de la semaine – days of the week (all seven days)
les jours de semaine aka les jours ouvrables – weekdays (5 jours: du lundi au vendredi)
le weekend

Interestingly:

lundi = this Monday, but le lundi = mondays.

Nous sommes samedi.	It's Saturday.
On peut aller au ciné vendredi.	We could go to the movies on Friday.	On va au ciné le vendredi.	We go to the movies on Fridays.
Je ne travaille pas (ce) lundi.	I'm not working on this Monday.	Je ne travaille pas le lundi.	I don't work on Mondays.

Dates

French dates follow the format of "day of the week, day of the month, month, year."

But the format is usually "le + day + day/date(numeric) + month + year" in writing and speaking.

Finally, le is used before the day and the number.