Prepositions of time "by" and "until"

In this English grammar lesson, you will learn the difference between the prepositions of time “by” and “until” and how to use them.

As a preposition of time, “by” means before a specific time.

“by” shows a time limit for something to happen.
An event must happen before a specific time is reached.

Please send me the report by Tuesday.
(I must receive it before Tuesday. The deadline is Tuesday)

Jane would like to lose 3 kg by June.
(She would like to lose 3kg before June.)

We often use “by” for projects with deadlines.

All job applications must be received by the 15th July.

We often use “by” to say when someone will return:

Mark: Where is Jane?
David: She is in London. She’ll be back by Saturday.

“by then”

We use “by then” to describe a specific time that we have already mentioned earlier in the sentence or in a previous sentence.

Tomorrow is the last day of school. You must finish all the exercises by then.

The TV show starts at 9pm so please finish your homework by then.

Preposition of time: “until”

As a preposition of time, “until” describes a continuous action that stops at a specific time.
“until” describes the duration of an action before a specific time.

I’m staying in New York until Friday.
I’m really tired. Last night I watched a film until midnight.
Mark lived in Manchester until 2010.

“till”

We can use “till” instead of “until“.
“till” is more informal.

I am going to study till 9 o’clock.
I am going to study until 9 o’clock.

Be careful of the spelling:

until
till

From …. until

from + specific time = start time
until + specific time = end time

The shop will be closed from 7pm until 8am tomorrow.
The shop will be closed from 7pm through 8am tomorrow. (USA English)

When NOT to use “until”

We do NOT use “until” to describe numbers or a quantity:

My car can take until 3 passengers.

Instead, we use “up to“:

My car can take up to 3 passengers.

You may take the accounting exam until 3 times.

You may take the accounting exam up to 3 times.

The cinema can hold until 100 people.
The cinema can hold up to 100 people.

The difference between “by” and “until”

I will be rich by 2020.

This means that in the present, I am not rich.
I predict that I will be rich before year 2020.

I will be rich until 2020.

This means that in the present, I am already rich.
I will continue to be rich between now and 2020
After 2020, I will no longer be rich. I will be poor.