Indicates a deadline or time limit by which an action must be completed. Used with verbs expressing completion or punctual actions.
Please submit the report by tomorrow.
Please submit the report by tomorrow.
Please come here by 5 o'clock.
I left early so I would make it in time for the 9 o'clock meeting.
We have to decide by next Friday.
before now; so far; until now
Combination of the particle まで ('until') and the particle に, forming an adverbial expression meaning 'by (a certain time)'.