How French works
The construction since + [date] is translated by depuis. Note that the tenses in French are different from those used in English:
Je fais mes études à Manchester depuis septembre 2000
I have been studying in Manchester since September 2000
Here whilst French uses the present tense (je fais), English uses the present perfect continuous (I have been studying). This happens in situations when the action is continuing, i.e. you started studying in September and are still doing so.
There is a similar difference when referring to actions taking place in the past:
Je faisais mes études à Manchester depuis septembre 1966
I had been studying in Manchester since September 1966
Here French uses the imperfect tense (je faisais) whilst English uses the past perfect continuous (I had been studying). This is because whilst the subject of the sentence is no longer studying, he / she was studying at the time the sentence refers to.
The construction for + [time period] can be translated by depuis or by il y a ... que and ça fait ... que, although these last two are generally restricted to spoken or more informal French. The same rules regarding tenses apply:
Tu as cette voiture depuis longtemps?
Il y a longtemps que tu as cette voiture?
Ça fait longtemps que tu as cette voiture?
Have you had this car for a long time?
This also applies to the construction voilà ... que (again restricted to spoken French), although it is generally not used in the interrogative :
Voilà 15 ans que j'ai cette voiture
I've had this car for 15 years
These tense rules do not apply where a negative is involved. Instead the tenses used are the same as in English:
Je ne l'ai pas vu depuis octobre
I haven't seen him since October
Il y a longtemps que je n'ai pas fait de ski
I haven't done any skiing for a long time
Note that in some cases where since begins a clause in the affirmative (as in It's been a year since I've been to France) the equivalent clause in French is in the negative (Ça fait un an que je n'ai pas visité la France). This is because in these sentences there is an implied negative: if the sentence were rewritten using for instead of since, a negative becomes necessary (I haven't been to France for a year). Consequently the sentence structure:
It is / it has been + [period of time] since [affirmative clause]
is rendered in French by:
Il y a / ça fait / voilà [period of time] que [negative clause]
Example:
It's been 5 years since we last met
Ça fait 5 ans que nous ne nous sommes pas revus
Pendant is used when expressing a completed action. The tenses used are the same as in English.
J'ai fait mes études à Manchester pendant quatre ans
I studied in Manchester for four years
Pendant is often omitted when used in front of a number when the verb has no other direct object :
Cette nuit j'ai dormi huit heures
Last night I had eight hours’ sleep
J'ai travaillé un an à Paris
I worked in Paris for a year
Pour is generally used instead of pendant when expressing a proposed duration in the future:
Je vais à Manchester pour une semaine
I am going to Manchester for a week
Je suis à Manchester pour une semaine
I'll be in Manchester for a week
However, pendant is generally preferred after the verb to be used in the future:
Je serai à Manchester pendant une semaine
I'll be in Manchester for a week
Note the use of dans instead of pendant where for has the sense of until:
Je ne serai pas à Manchester que dans quelques semaines
I won't be in Manchester for a few weeks
These conjunctions take the indicative and not the subjunctive . Pendant que is followed by the same tenses as in English:
Il a beaucoup changé pendant qu'il était à Manchester
He changed a lot when he was in Manchester
Depuis que is followed by the present tense if the action of the verb is continuing:
Il est devenu beaucoup plus indépendant depuis qu'il est étudiant
He's become much more independent since he's been a student
Depuis que je suis ici je n'ai vu personne
Since I've been here I've seen no-one
Sometimes the difference between a continuing and a completed action can be hard to differentiate, as the meaning can be the same:
Depuis que Pierre a pris la retraite / est à la retraite, il est beaucoup moins fatigué
Since Pierre retired / has been retired, he's a lot less tired
This construction is followed by the present tense when English uses the perfect tense:
C'est la première fois que vous venez en Angleterre?
Is this the first time you've been to England?
C'est la première fois que je n'assiste pas à une réunion
It's the first time I haven't attended a meeting
This contrasts with the construction le premier (+ noun) ... que which is followed by the subjunctive (see 23.1.1.1).