# Bus doesn't leave for about 36 hours

A: Hi. When does the next bus leave?
B: Bus doesn’t leave for about 36 hours.
Question: Bus doesn’t leave “for” about 36 hours.
The preposition here must use “for”? not “in”?

Thank you!

The bus will leave in two hours.
=it will leave when two hours have passed. It might leave before two hours pass.

The bus will not leave in two hours.
=It will leave in more than two hours.

The bus wil not leave for two hours.
=It will not leave until two hours pass.

Am I right?

The expression is ‘not for’ rather than ‘not in,’ so yes, the preposition must be ‘for’ rather than ‘in.’

in a given period of time = after a given period of time has passed

In the affirmative, “the bus leaves in about 36 hours” has useful meaning. It means that the bus will depart after approximately 36 hours have passed. For example, the bus is scheduled to depart at 10:50 pm tomorrow and it is around 10:30 am now.

However in the negative, it does not convey any useful information. If you said, “The bus doesn’t leave in about 36 hours,” you would be saying that the bus will not be leaving after approximately 36 hours have passed. No native English speaker would normally ever say this, unless maybe that person were joking around.

not for a given period of time = not until a given period of time has passed = not before a given period of time has passed

“The bus doesn’t leave for about 36 hours” means that the bus will not depart until approximately 36 hours have passed. It will not depart before approximately 36 hours have passed. It has the same approximate meaning as “the bus leaves in about 36 hours.” It can be used in the exact same scenario: The bus is scheduled to depart at 10:50 pm tomorrow and it is around 10:30 am now.

So, short answer: relative to time, “not for” has the same approximate meaning as “in.”

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Another example:

— The new Star Wars movie is out. You said you would take me today. When are we going? When are we going?

— That movie doesn’t start for another three hours. So quit bugging me.

“That movie doesn’t start for another three hours.” = It will be another three hours before that movie starts. = That movie will not start until another three hours have passed. = That movie will not start before another three hours have passed. = The next scheduled movie time is three hours from now. = That movie starts in three hours.

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