Time Clauses

Form

A time clause says when the other half of the sentence happens, and it opens with a conjunction such as when, before, after, while, until, as soon as, once, since or by the time.

The rule learners break most often is simple: never put will inside a time clause, because the present simple already carries the future meaning (I will call you as soon as I arrive, not as soon as I will arrive). With two past events, the earlier one can take the past perfect (By the time the movie started, we had eaten all the popcorn), and while usually pairs with a longer background action (While she was cooking, her phone rang). When both halves share a subject, the clause can shrink to a participle phrase (After finishing his degree, he moved to Japan).

When to Use It

1. 1

   Use the present simple after a time conjunction even when you mean the future

   I will call you as soon as I arrive.

2. 2

   Use until for the point where an action stops, and by for a deadline

   The shop is open until ten.

3. 3

   Use while with a longer action in the background, and when with a short one

   While she was cooking, her phone rang.

4. 4

   Use during in front of a noun and while in front of a clause

   I met a lot of people during my trip to Spain.

5. 5

   Use the past perfect for the earlier of two past events, especially after by the time

   By the time we arrived, the show had started.

6. 6

   Shrink the clause to a participle phrase when both halves share a subject

   After finishing his degree, he moved to Japan.

Common Mistakes

• Will inside the time clause: write I will text you when I arrive, not I will text you when I will arrive — after a time word the present simple carries the future.
• During for while: write while we were waiting, not during we were waiting — during goes in front of a noun, and while in front of a clause.
• Until for by: write Please finish it by Friday, not Please finish it until Friday — by marks a deadline, and until marks a stretch of time.
• Since without a perfect tense: write I have been playing volleyball since I was a teenager, not I play volleyball since I was a teenager — since needs a perfect tense in the main clause.
• A past tense in the -ing phrase: write After finishing the report, she went home, not After finished the report, she went home — the shortened clause takes the -ing form and has no subject of its own.