Prepositions of Time: at, in, on

Prepositions of Time: at, in, on

We use:
-at for a PRECISE TIME
-in for MONTHS, YEARS, CENTURIES and LONG PERIODS
-on for DAYS and DATES

AT

PRECISE TIME
at 3 o'clock
at 10.30am
at noon
at dinnertime
at bedtime
at sunrise
at sunset
at the moment

in
MONTHS, YEARS, CENTURIES and LONG PERIODS
in May
in summer
in the summer
in 1990
in the 1990s
in the next century
in the Ice Age
in the past/future

on
DAYS and DATES
on Sunday
on Tuesdays
on 6 March
on 25 Dec. 2010
on Christmas Day
on Independence Day
on my birthday
on New Year's Eve

Look at these examples:
-I have a meeting at 9am.
-The shop closes at midnight.
-Jane went home at lunchtime.
-In England, it often snows in December.
-Do you think we will go to Jupiter in the future?
-There should be a lot of progress in the next century.
-Do you work on Mondays?
-Her birthday is on 20 November.
-Where will you be on New Year's Day?

Notice the use of the preposition of time at in the following standard expressions:

Expression Example

at night The stars shine at night.

at the weekend I don't usually work at the weekend.

at Christmas/Easter I stay with my family at Christmas.

at the same time We finished the test at the same time.

at present He's not home at present. Try later.

Notice the use of the prepositions of time in and on in these common expressions:

in
in the morning
in the mornings
in the afternoon(s)
in the evening(s)

on
on Tuesday morning
on Saturday mornings
on Sunday afternoons
on Monday evening

When we say last, next, every, this we do not also use at, in, on.
-I went to London last June. (not in last June)
-He's coming back next Tuesday. (not on next Tuesday)
-I go home every Easter. (not at every Easter)
-We'll call you this evening. (not in this evening)