depuis, pendant, il y a

CEFR A2Taught in Module 12, Mon parcours

Three ways to put a duration on an event. Choosing between them is about whether the situation is finished.

depuissince / for — still true nowJ'habite ici depuis trois ans.
pendantfor — a finished stretchJ'ai travaillé là pendant deux ans.
il y aago — a point in the pastJe suis arrivé il y a trois ans.

The tense follows from the choice, and this is the part English speakers get wrong:

  • depuis takes the present, because the situation is still going on. J'apprends le français depuis six mois. — I have been learning French for six months (and still am). English uses a past form here; French does not.
  • pendant takes the passé composé, because the stretch is over. J'ai étudié pendant six mois. — and then I stopped.
  • il y a takes the passé composé, because it dates a single event. Il est parti il y a deux jours.

To ask, use depuis quand (since when) or depuis combien de temps (how long):

  • — Vous habitez ici depuis combien de temps ?
  • Depuis deux ans.

Do not confuse this il y a with the il y a meaning there is. Same words, and only the presence of a duration after it tells them apart: il y a un problème (there is a problem) versus il y a un mois (a month ago).

Knowing the rule is not the same as producing it.

This page explains the pattern. The track drills it: the point arrives inside a mini-dialogue, then production marked against a CEFR descriptor, then a module test that returns you to your two weakest sessions if you miss it.