They are used to describe how long you have been doing something for, since …, or ____ (amount of time) ago

Depuis

Depuis is a French preposition meaning “for” or “since” when followed by a reference to time. It is used with the present tense (it can also be used with an event and the imperfect tense).

~With a given period of time = _____ has/d been happening for that amount of time.
~With a specific point in time = _____ has/d been happening since that time/event.

Par exemple…

J’étudie depuis deux heures.		I’ve been studying for two hours.
Elle t’écoute depuis 8h15.		She’s been listening to you since 8:15.

Note that there is no French equivalent for these verbal constructions. “Has been happening” must be translated by the present, while “had been happening” is the imperfect.

Il y a

Past tense + il y a + amount of time indicates that something happened that amount of time ago.

Par exemple…

J’ai mangé il y a une heure.		I ate an hour ago.
Nous sommes revenues il y a une semaine.		We came back a week ago.
Elle a joué au foot il y a 15 minutes.		She played soccer 15 minutes ago

Sommaire: Depuis vs Il y a

Ago

• Past tense + il y a + period of time

For/ Since

• Present tense + depuis + period of time