Ch 15
Prepositions of Time
in January · on Monday · at 8 o'clock
The same three prepositions tell us WHEN. Each one has a clear rule.
in
months, years, seasons, parts of the day: in January, in 2025, in winter, in the morning
on
days and dates: on Monday, on 25th December, on my birthday
at
specific times and night: at 8 o'clock, at midnight, at the weekend, at Christmas
Months
in January, in June, in December
Seasons
in spring, in the summer
Centuries
in the 21st century
Parts of day
in the morning, in the afternoon, in the evening
Note: "in the morning" but "at night" — this is an irregular exception, just memorise it.
Days
on Monday, on Friday, on Saturdays
Dates
on 14th March, on December 25th
Special days
on my birthday, on Christmas Day, on New Year's Day
Day + part
on Monday morning, on Friday night
"in the morning" but "on Monday morning" — when you add a day name, the preposition becomes "on".
Clock times
at 8 o'clock, at 7:30, at midnight, at noon
Night
at night (NOT in the night)
Weekends (UK)
at the weekend (US: on the weekend)
Holidays
at Christmas, at Easter (the whole period)
Meal times
at lunch, at dinner, at breakfast
I will see you in Monday.
→
I will see you on Monday.
on + day name
She gets up at 7 o'clock in the morning on Monday.
→
...at 7 on Monday morning.
on Monday morning = day+part
I sleep in the night.
→
I sleep at night.
at night (exception)
My birthday is in 25th April.
→
My birthday is on 25th April.
on + specific date
Recap
in
long periods (months, years, seasons, parts of day)
in 2025, in January, in the morning
on
days and dates
on Monday, on 25th December
at
specific times, night, weekends
at 8pm, at night, at Christmas
Memory aid
small → at · medium → on · large → in
time gets bigger left to right