For clock times we use at, but not usually in the
What time are you leaving for Germany? ~ I shall
try to leave at three o' clock.
on for time
For days, dates and times like Sunday evening
or Saturday morning, we use on:
I usually do my homework on Sunday evening; on Saturday
morning I'm normally at the gym.
Can we do it on Thursday? ~ No, not on Thursday.
I'm in Leeds all day on Thursday.
My birthday is on 26th December and then Mark arrives on
(Note that we write on 27th December, but we say on the
27th of December.)
in for time
For centuries, years, seasons, months,
weeks, and for time phrases such as in the afternoon,
or in the evening we use in:
In the 17th Century, 200,000 people were executed in
America for practising witchcraft.
Brazil first won the World Cup in 1958 and then again in
1962, but in 1966 it was England's turn.
I prefer to take my holidays in the spring and autumn
and work in summer when everybody else is on holiday.
I've got my final exams in May. When in May? In
the final week of May.
I work best in the morning. I'll work again in the evening
if I have to, but I prefer to relax in the afternoon.
(But note we say at the weekend, at Christmas, at
Easter and at night.)
Note also subtle the difference in meaning between the expressions
in time (which means before a given time) and on time
(which means exactly at that time):
The 7.53 is always on time, but yesterday it was late.
I couldn't get there in time for the beginning of Jo's
concert and missed the opening number.