In / On / At (Time)
From large periods to exact points in time.
Rule
In is for large time periods, on is for days and dates, and at is for exact times or fixed moments.
Formula
| In: centuries / decades | large time periods | in the 1900sin the 90s |
|---|---|---|
| In: years / months | a year or month | in 2026in April |
| In: seasons / long periods | a season or long period | in summerin the future |
| In: parts of the day | a general part of the day | in the morningin the evening |
| In: after a period | after some time passes | in a weekin two hours |
| On: days / dates | a weekday or date | on Mondayon April 3rd |
| On: specific days | a special day | on my birthdayon New Year's Day |
| On: day + part of day | a specific day + part of day | on Sunday morningon Friday evening |
| On: holidays with day | holiday + the word day | on Easter Dayon Christmas Day |
| At: exact time | exact clock time | at 8 a.m.at 6:30 |
| At: exact moments | a very specific moment | at midnightat the moment |
| At: holidays without day | a holiday as a period | at Easterat Christmas |
| At: fixed expressions | fixed expressions | at nightat the weekend |
Notes
- in the morning, but at night
- on Monday morning because the day is specific
- British English often uses at the weekend; American English uses on the weekend
- No preposition: today, tomorrow, yesterday, last week, next year