Time Clauses: When, Until, As Soon As & Before
Level B1 · Tenses
After words like when, while, before, after, until, and as soon as, English uses a present tense to talk about the future — never will — even though the whole sentence is about something that hasn't happened yet. I'll call you when I arrive is correct; I'll call you when I will arrive is wrong, even though "arrive" clearly refers to a future moment. The will only belongs in the main clause, the one stating the actual future action.
The same present-tense rule applies to every time connector:
- when / as soon as — for the moment something happens: I'll text you when I land; She'll start cooking as soon as she gets home.
- before / after — for the order of two future events: Finish your homework before you watch TV; We'll leave after the rain stops.
- until / till — for a future action continuing up to a point: I'll wait here until you're ready.
- by the time — for a deadline, often paired with the future perfect in the main clause: By the time you arrive, I will have finished cooking.
- if you need a completed action before the other starts, use the present perfect instead of the present simple: I'll call you when I've finished the report (finished first, then call) — not when I finish, which suggests the two happen at almost the same moment.
The most common mistake is putting will (or would, in reported/past contexts) inside the time clause itself — I'll call you when I will arrive and She said she'd call when she would arrive are both wrong; the time clause always uses a present (or present perfect) form, and will only appears once, in the main clause: I'll call you when I arrive; She said she'd call when she arrived. A second mistake is treating these connectors like if — if introduces a condition that might not happen, but when/as soon as/before/after/until treat the future event as certain, so mixing up if I will arrive and when I arrive is really a tense mistake layered on top of a meaning mistake.
Look for when, while, before, after, until/till, as soon as, or by the time introducing a clause about the future — if the verb in that clause is will/would, it's wrong; it should be a plain present form (or present perfect, if that action needs to finish before the other one starts).