1. DEPUIS, IL Y A, PENDANT, POUR QUAND, LORSQUE
Temporal expressions

2. Depuis
Depuis, meaning "for" or "since," can be used in the present or past in order to express an action that began in the past and continued to the temporal reference point used in the sentence: either the present or some point in the past. Depuis is thus used for actions that were incomplete at the referenced time, and can refer to two different kinds of time: 1) When followed by a period of time, depuis indicates the duration of an action and is equivalent to "have been + -ing (perfect progressive) + for"* Nous attendons depuis une heure. We've been waiting for an hour. Il parle depuis 5 minutes. He's been speaking for 5 minutes. Il travaillait depuis 10 jours quand je l'ai vu. He'd been working for 10 days when I saw him. 2) When followed by an event or point in time, depuis indicates the start time of an action and is translated in English by "have + -en/-ed (perfect tense) + since/for" Je suis malade depuis mon arrivée. I've been sick since I got here.
Il était fâché depuis l'annonce, mais maintenant... He had been angry since the announcement, but now... Depuis hier, je suis déprimée. I've been depressed since yesterday. Il ne fume pas depuis un an. He hasn't smoked for a year.

3. Il y a
Il y a means "ago" and can only be used for things that are already completed. The verb in the sentence must be in the past and il y a must be followed by some reference to time.** Je suis arrivée il y a une heure. I arrived an hour ago. Il a travaillé il y a 10 jours. He worked 10 days ago. J'étais malade il y a une semaine. I was sick a week ago. Il y a deux jours, j'ai vu un chat noir. Two days ago, I saw a black cat. J'ai déménagé ici il y a longtemps. I moved here a long time ago. *Il y a ... que, ça fait ... que , and voilà ... que are informal equivalents for the first use of depuis - they mean "have been doing for a certain amount of time." Il y a cinq ans que j'habite ici. I've been living here for five years. Ça fait deux heures que nous attendons. We've been waiting for two hours. Voilà six mois que je travaille avec Marc. I've been working with Marc for six months. **Voilà can also replace il y a, informally. Il est parti voilà deux heures. He left two hours ago.

4. Pendant Tu ne peux pas étudier pendant que tu écoutes les infos.
Pendant means "for" and refers to the entire duration of an action in the past or future, with no relation to the present. Pendant combien de temps avez-vous étudié le français ? How long did you study French? J'ai étudié le français pendant 3 ans. I studied French for 3 years (and then stopped). Je vais habiter en France pendant 2 mois. I'm going to live in France for 2 months. Pendant followed by a noun means "during." In this sense, it is synonymous with durant. J'ai vu un film pendant mon séjour. I saw a film during my stay. Pendant ce temps, il m'attendait. During this time, he waited for me.
Pendant que : 2 actions simultaneously:
Pendant que je suis à Paris, je visite autant de musées que possible
Tu ne peux pas étudier pendant que tu écoutes les infos.

5. Pour
Pour can express the duration of an event only in the future. Note that pendant could also be used in all of these. Je vais y habiter pour/pendant 2 mois. I'm going to live there for 2 months. Il étudiera en Europe pour/pendant 3 ans. He'll study in Europe for 3 years. Le projet est suspendu pourun an. The project is suspended for a year. Although the verb in the final example is not in the future, the use of pour indicates that the one-year suspension is either about to start or is currently underway. If the suspension had already occurred, you would have to use pendant: Le projet a été suspendu pendant un an. The project was suspended for a year.

6. Quand vs. lorsque
Quand and lorsque both mean "when." 1) temporal correlation (interchangeable with lorsque) Je marchais quand tu m'as téléphoné. I was walking when you called me. Quand je t'ai vu, j'avais peur. When I saw you, I was afraid. Je te verrai demain quand j'arriverai.* I will see you tomorrow when I arrive. 2) repeated correlation (meaning chaque fois que) Quand il est là, elle ne parle pas. When(ever) he is there, she doesn't speak. Quand il sera là, elle ne parlera pas.* When(ever) he is there, she won't speak. 3) Interrogative adverb Quand vas-tu arriver ? When are you going to arrive? Je ne sais pas quand il reviendra. I don't know when he will return.

7. Lorsque
1) temporal correlation (interchangeable with quand) Je marchais lorsque tu m'as téléphoné. I was walking when you called me. Lorsque je t'ai vu, j'avais peur. When I saw you, I was afraid. Je te verrai demain lorsque j'arriverai.* I will see you tomorrow when I arrive. 2) simultaneous opposition (meaning alors que or tandis que) J'ai crié lorsqu'il a fallu courir. I screamed when/whereas I should have run. Je crierai lorsqu'il faudra courir.* I'll scream, when/whereas I should run. *Note: When the action that follows lorsque or quand has not yet occurred, the French verb that follows must be in the future, whereas in English the present tense is used.

8. Summary Ago Have -ed for/since Have been -ing for Depuis vs Il y a
Informal synonyms
voilà
il y a que, ça fait que, voilà que
French verb tense
past
present or past
present
Reference to time
period of time
point in time
Type of action
completed
continuing