Prepositions · CEFR A1
“In Monday” or “on Monday”? Prepositions of time
Incorrect
in Monday
Correct
on Monday
Use “on” with days: on Monday, on Friday evening, on 3 May. Use “in” for months, years and seasons, and “at” for clock times.
The rule
at - times and short points: at 7 o’clock, at noon, at the weekend (UK).
on - days and dates: on Tuesday, on my birthday, on 14 February, on the weekend (US).
in - longer periods: in March, in 2026, in summer, in the morning.
No preposition before this, next, last, every: next Monday, every Friday.
Examples
✗ See you in Monday.
✓ See you on Monday.
✗ I have class in Tuesday morning.
✓ I have class on Tuesday morning.
Specific day + part of day = on
✗ We met on next Friday.
✓ We’ll meet next Friday.
Why learners make this mistake
Different languages divide time differently - Spanish uses el lunes with no preposition, Portuguese na segunda, German am Montag - so English in/on/at feels arbitrary.
Remember
From big to small: IN a month, ON a day, AT a time.
Frequently asked questions
- Is it “on the weekend” or “at the weekend”?
- Both are correct: “at the weekend” is British English and “on the weekend” is American English.
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