English grammar: Prepositions of time

What this grammar point covers

Prepositions of time are words that show when something happens. They connect events to times, like days, months, or specific moments.

When to use it

Use these prepositions to talk about when something happens, how long it lasts, or when it starts and ends.

Key forms

• in (in the morning, in 2020)
• on (on Monday, on July 4th)
• at (at 5 o'clock, at night)
• by (by Friday, by 8 pm)
• until (until tomorrow, until next week)
• since (since 2010, since noon)
• for (for two hours, for a week)

Examples

Tips

• Use 'at' for precise times, 'on' for days and dates, and 'in' for longer periods like months or years.
• Do not use 'in' with 'morning', 'afternoon', or 'evening' if you add a specific day: say 'on Monday morning'.
• Be careful: 'at night' (not 'in night').

Exceptions and edge cases

• We say 'at the weekend' in British English, but 'on the weekend' in American English.
• Use 'at Christmas' (for the holiday), but 'on Christmas Day' (for the specific day).