samedi vingt-et-un décembre deux mille dix.
Sept decembre 2010
Samedi is how you say Saturday in French.
You would say "samedi prochain" in French to refer to next Saturday.
"qu'est-ce que vous (faites) samedi" means "what are you (doing) on Saturday?" in French.
Samedi soir
It would be "Le samedi." However if you want to say next Saturday it would be "Le samedi prochain."
How to say on Saturday I went on a tour
Ce Samedi - if it's this Saturday Le Samedi - if it's Saturday's in general.
To say "my favorite month is December" in French, you would say, "Mon mois préféré est décembre." This phrase captures your preference for the month of December.
It would be correct to say "On the 13th December 2010"
Décembre
Je serai de retour samedi