There are three prepositions of time:
At
‘At’ is used for precise times:
At ten o’clock.
At 10.30am.
At the moment/present/same time.
At sunrise/sunset/noon/dinnertime/bedtime/dusk/dawn.
Note: At night is a standard expression that is an exception in this case.
In
‘In’ is used for months, years, decades, centuries, and long periods of time:
In January.
In 1991.
In the 70s.
In this century.
In the Dark Ages.
Note: In the morning(s)/afternoon(s)/evening(s) are standard expressions that are exceptions in this case.
On
‘On’ is used for days and dates:
On Wednesday.
On Friday.
On the 10th of January
On Christmas.
Note: ‘on’ is also used when you specify the day followed by the part of the day. For example on Wednesday mornings.
Tags:
Spoken English