By vs until

Both go with a point in time, but they look at it in two different ways.

💡Ask yourself: does the action continue all the way to that time, or does it just need to be done before it? Continues → until. Deadline → by.

1. by + time = at or before that time

• I need the report by Friday.

• Dinner will be ready by seven.

• The parcel should arrive by the end of the week.

2. by then / by that time / by now

• Call me at nine. I'll be home by then.

• They left at noon, so they should be in Da Lat by now.

3. Often used with perfect tenses (see the lesson “Future perfect”)

• By next summer, I'll have saved enough for a motorbike.

• By 2020, she'd moved to Saigon.

1. A situation continues up to a time, then stops. Till = until, common in speech.

• The shop is open until 10 pm.

• Let's wait here until the rain stops.

• I work from nine till five.

2. not … until = not before (later than expected)

• I didn't get home until midnight.

• The film doesn't start until eight.

3. until + clause: present tense for the future (not will)

• Stay here until I come back.

  not: until I will come back

• I'm not leaving until I've finished this chapter.

By the time + clause = “when this happens, the other thing has already happened”. The main clause often uses a perfect tense, because that action comes before the time.

• By the time I found my keys, the bus had already left.

• By the time you read this, I'll be on the plane.

  not: By the time you will read

💡Don't say “until the time” with this meaning. For “when …, something had already happened”, always use by the time.

• You can stay until Sunday.

  you stay the whole time up to Sunday

• You have to leave by Sunday.

  you leave on or before Sunday

• I'll be at work until six, so I'll be home by half past six.

• I can't finish it by Friday.

  I'll miss the deadline

• I won't finish it until Friday.

  it will be done on Friday, not earlier

• ✗I have to finish this essay until Monday.

  ✓I have to finish this essay by Monday.

  Deadline for finishing → by.

• ✗We stayed at the party by midnight.

  ✓We stayed at the party until midnight.

  Staying continues up to the time → until.

• ✗Until the time I got to the station, the train had left.

  ✓By the time I got to the station, the train had left.

  Fixed phrase: by the time.

• ✗By the time you will arrive, we'll have eaten.

  ✓By the time you arrive, we'll have eaten.

  Use the present after by the time for the future.

• ✗By the time we arrived, the shop closed.

  ✓By the time we arrived, the shop had closed.

  The earlier action → past perfect.