By shows a time limit for something to happen - an event must occur before a certain time is reached. For example:
- You need to finish this report by Monday.
- I'll be back by six o'clock.
- Our business will be making a profit by next March.

There are three common phrases used with by:

By the time
I want to be a successful businessman by the time I'm 30.
By the time we arrive at the station, the train will be gone.

By then
They have four months to prepare for the soccer game, so by then they should be a strong team.
The deadline for giving your essay is next Monday at 4.00. If I don't receive your essay by then, it won't be marked.

By that time
We finished work at 9.00, but by that time it was too late to go out.
I hope to go abroad next year, and by that time I'll have enough money.

Until means an action or situation continues up to a certain time. For example:
- We were working last night until 2.30.
- You can stay at home until you feel better.
- Can you wait until I'm ready?

Compare until and by:
- "I'll work here until September." This means I keep working here to September, then I stop.
- "I'll work here by September." This means that I'm not working here now, but sometime between now and September I will start.

Till is another form of until, the meaning is generally the same although until is usually used at the beginning of a sentence.

From ... to/until is used to mark the beginning and end of a period of time. For example:
- Western people often work from Monday to Friday, but Oriental people often work from Monday to Saturday.
- I'm staying in Saudi Arabia from the beginning of March until the end of August.
From ... to is slightly more informal than from ... until.

-----