Adverbial clauses of time consist of two clauses: the main clause and the time clause. The time clauses begin with: when, whenever, while, as, since, after, before, until, as soon as, once…
Since means from that time. We commonly use the Present Perfect and the Present Perfect Continuous with since. Here, we indicate a specific point of time.
I have been studying English since 2010.
We commonly use the Present Perfect and the Present Perfect Continuous with for. Here we indicate a length of time.
Sam has helped me for six hours.
While and As mean during that time. These two words usually use with the Past Continuous because the meaning of during that time which indicate that an action in progress.
He finished dinner while I was doing my homework.
As I was doing my homework, he finished dinner.
- By the time
By the time expresses the idea that one event has been completed before another. It's important to notice the use of the Past Perfect for past events and the future events in the main clause.
By the time he came home, I had finished my house work.
We will have finished our lunch by the time they arrive.
Until and Till express up to that time. We use either the Simple Present or Simple Past with until and till. Till is usually use in spoken English.
I waited until my father finished his office work.
He will wait at the school till you come.
- As soon as
As soon as means when something happens immediately afterwards. One event will occur immediately after the other event. We usually use the Simple Present for future events, although Present Perfect can also be used.
He will tell us as soon as he gets the news.
He will tell us as soon as he has got the news.