We use by with a point in time.
The car will be ready by Friday. (= Friday or earlier)
The accounts will be finished by the end of the month. (= end of the month or earlier)
The work was done by 6pm. (=6pm or maybe it was finished earlier)

We use until for the end of a period of time.
It rained until Friday. (= for a period of time and stopped on Friday.)
I'll be busy until 3.30pm. (for the period of time up to 3.30. After 3.30 I won't be busy).
We'll be working hard until 6pm. (= for the period of time up to 6pm. After 6pm we won't be working hard.)

Write the missing words.
I have to be home
5pm tonight. We're going out for dinner. If I am home 5 I'll have 6.30pm to have a shower and get dressed. I have to buy some flowers on the way. The florist (flower shop) is open 7pm. I'll be at the restaurant 7.15.

Go back to Intermediate.