Preposition 'At', 'In' and 'On' (Prepostions of Time)

'At', 'in' and 'on' are prepositions that are used for two varying purposes. They can be used as prepositions of 'place' or 'time'. 

Let us look at 'at', 'in' and 'on' as prepositions of time.

We use:

• at - for a PRECISE TIME

• in - for MONTHS, YEARS, CENTURIES and LONG PERIODS

• on - for DAYS and DATES

at PRECISE TIME	in MONTHS, YEARS, CENTURIES and LONG PERIODS	on DAYS and DATES
at 3 o'clock	in May	on Friday
at 10.30 a.m.	in winter	on Fridays
at noon	in the winter	on 6 March
at lunchtime	in 2015	on 25 May, 2015
at bedtime	in the 1980s	on Christmas Day
at sunset	in the next century	on Independence Day
at the moment	in the past/future	on New Year's Eve

Look at  the examples below:

• Bukky left the office at lunchtime.
• The driver returns home mostly at midnight.
• The staff meeting begins at 10 o' clock.
• My son wants to be an astronaut in the future.
• In Nigeria, it often rains in May.
• The firm has undergone great progress in the past decade.
• I do not work on Saturdays.
• He promised to come around on Christmas' Eve.
• Joan's birthday is on 17 October.

Note 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'll see you at Christmas.
at the same time	They completed the work at the                    same time.
at present	He's not home at present.

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

in	on
in the morning	on Friday morning
in the mornings	on Saturday mornings
in the afternoon(s)	on Sunday afternoon(s)
in the evening(s)	on Monday evening(s)

When we use last, next, every, this as adjectives before nouns, we do not also use at, in, on.

Examples:

• He travelled to Kano last June. (not in last June)

• He's coming back next weekend. (not at next weekend)
• He visits his uncle every Christmas. (not at every Christmas)
• Will you be around this evening? (not in this evening)