in + month / year / season / part of the dayUse in with larger time periods, not with one day or one exact clock time.
Prepositions of Time
A1Use in for months and years, on for days and dates, and at for exact times and holidays.
What you'll learn
- Use in with months, years, seasons, and parts of the day.
- Use on with days of the week and dates.
- Use at with clock times and exact moments.
- Use at with holidays when you mean the holiday period.
- Pick the preposition from the kind of time expression.
Structure
on + day / dateUse on with a specific day or date.
at + time / holidayUse at with exact times and holiday periods.
Build a sentence
Time expression
Preposition
inSeptember
Maria starts her course in September.
Month = in.
When to use
Long periods
Use in with bigger time blocks: in May, in 2026, in summer, in the morning.
One day
Use on for one named day or one date: on Tuesday, on July 4, on my birthday.
Exact time
Use at for exact points on the clock or short fixed moments: at 7:15, at noon, at night.
Holiday period
Use at for the holiday period as a whole: at Christmas, at Easter.
Markers
JanuaryFridayAugust 157:30noonChristmasnightsummer
Common mistakes
Wrong
Maria starts her course on September.
Correct
Maria starts her course in September.
September is a month, so use in.
Wrong
Lisa has yoga in Friday.
Correct
Lisa has yoga on Friday.
Friday is a day of the week, so use on.
Wrong
Dmitri wakes up in 6:30.
Correct
Dmitri wakes up at 6:30.
6:30 is an exact clock time, so use at.
Wrong
We visit family on Christmas.
Correct
We visit family at Christmas.
When you mean the whole holiday period, use at.
Wrong
Anna calls me at Monday.
Correct
Anna calls me on Monday.
Match the preposition to the time word: Monday is a day, so use on.
Common misconceptions
❝ I can use one time preposition for every kind of time expression. ❞
English changes the preposition with the type of time expression: in for larger periods, on for days and dates, at for exact times and holidays.
❝ Holiday names always take on because they feel like days. ❞
Use at when you mean the holiday period as a whole: at Christmas, at Easter.
Skills in this rule (5)
IN_FOR_MONTHS_YEARSw5Use in with months, years, and longer time periods
Use in before months, years, seasons, and parts of the day. It answers when something happens inside a larger time period.
ON_FOR_DAYS_DATESw5Use on with days and dates
Use on before days of the week and calendar dates. It answers when something happens on a specific day.
AT_FOR_CLOCK_TIMESw5Use at with clock times and exact moments
Use at before clock times and short exact points such as noon, midnight, and night. It answers when something happens at one precise time.
AT_FOR_HOLIDAYSw4Use at with holidays as time points
Use at with holidays when you mean the holiday period as a whole, such as at Christmas or at Easter.
CHOOSE_TIME_PREPOSITIONw5Choose in, on, or at from the time expression
Look at the time word first: month or year = in, day or date = on, exact time or holiday period = at.