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English grammar

The moment, once, by the time: time clauses and their tenses

C1 · Advanced Joining sentences Questions 10

The rule

Beyond when and after, English has time conjunctions with precise meanings. the moment, the minute, as soon as = immediately; once = after, and because; by the time = not later than, usually with a perfect in the main clause (By the time we arrived, the film had started; By the time you read this, I will have left); until = up to (and not … until for delay); every time / whenever; the next time; now that = because now; as for two things changing together (As the day went on, it got colder). In a time clause about the future, English uses the present or present perfect, never will: Once you have signed, we will start, I’ll call the moment I get the results. Confusing until with by or since is a classic error at every level.

Pattern

the moment / the minute / as soon as / once + present (perfect) for the future · by the time + past → past perfect · + present → will have done · (not) … until · now that · as (things change together)

Examples

  1. The moment she walked in, everyone stopped talking.

  2. Once you have signed the contract, we can begin.

  3. By the time we got to the station, the train had left.

  4. Now that the children have left home, the house feels enormous.

Common mistakes

  • Wrong: Once you will finish, call me.

    Right: Once you have finished, call me.

    A future time clause takes the present (perfect), not will.

  • Wrong: By the time we arrived, the film already started.

    Right: By the time we arrived, the film had already started.

    by the time + past usually needs the past perfect in the main clause.

  • Wrong: We will wait since he arrives.

    Right: We will wait until he arrives.

    until = up to a moment; since measures from a starting point.

Practice questions

Try each one yourself first, then open “Show answer” for the solution and the reason.

  1. 1Fill in the gap.

    I’ll call you the moment I _____ the results.

    1. would get
    2. get
    3. am going to get
    4. will get
    Show answer

    Answer: B I’ll call you the moment I get the results.

    A future time clause: present simple.

  2. 2Choose the correct sentence.

    1. By the time you read this, I leave the country already.
    2. By the time you are reading this, I had left the country.
    3. By the time you will read this, I will leave the country.
    4. By the time you read this, I will have left the country.
    Show answer

    Answer: D By the time you read this, I will have left the country.

    by the time + present → future perfect in the main clause.

  3. 3Choose the correct sentence.

    What does the sentence mean?

    Once the snow melts, the pass will reopen.

    1. The pass reopened when the snow melted once.
    2. The pass will stay closed after the snow melts.
    3. The snow melted only one time.
    4. The pass will reopen after the snow has melted.
    Show answer

    Answer: D The pass will reopen after the snow has melted.

    once = as soon as, after.

  4. 4This sentence is wrong. Choose the fix.

    We won’t leave since everyone is ready.

    1. We won’t leave until everyone is ready.
    2. We won’t leave by everyone is ready.
    3. We won’t leave until everyone will be ready.
    4. We won’t leave while everyone is ready.
    Show answer

    Answer: A We won’t leave until everyone is ready.

    not … until: the leaving waits for the moment everyone is ready.

  5. 5Change the sentence.

    Join with by the time.

    The police arrived. The thieves had already escaped.

    1. By the time the police arrived, the thieves had already escaped.
    2. By the time the police had arrived, the thieves already escape.
    3. By the time the police arrive, the thieves already escaped.
    4. By the time of the police arriving, the thieves escaped already.
    Show answer

    Answer: A By the time the police arrived, the thieves had already escaped.

    by the time + past simple, past perfect in the main clause.

  6. 6Choose the correct sentence.

    1. Now that you are mention it, I did see him leave early.
    2. Now that you mention it, I did see him leave early.
    3. Now that you mention it, I did saw him leave early.
    4. Now you that mention it, I did see him leave early.
    Show answer

    Answer: B Now that you mention it, I did see him leave early.

    now that = because now.

  7. 7Choose the correct sentence.

    What does the sentence mean?

    As the evening went on, the guests grew louder.

    1. The guests were loud because it was evening.
    2. The guests got louder gradually.
    3. The guests stopped being loud.
    4. The guests left as soon as it was evening.
    Show answer

    Answer: B The guests got louder gradually.

    as + a change = gradually, at the same time.

  8. 8Fill in the gap.

    She had _____ sat down than the phone rang.

    1. as soon
    2. the moment
    3. hardly
    4. no sooner
    Show answer

    Answer: D She had no sooner sat down than the phone rang.

    no sooner … than is a fixed pair.

  9. 9Put the words in the right order.

    Every time I wash the car it rains

    Show answer

    Answer: Every time I wash the car it rains.

    every time = whenever.

  10. 10Choose the correct sentence.

    Which sentence means the same?

    I’ll believe it when I see it.

    1. I believe it now that I have seen it.
    2. I saw it, so I believe it.
    3. I won’t believe it until I see it.
    4. I will see it after I believe it.
    Show answer

    Answer: C I won’t believe it until I see it.

    The belief waits for the seeing: not … until.

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