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 in
MONTHS, YEARS, CENTURIES and LONG PERIODS on
DAYS and DATES
at 3 o'clock in May on Sunday
at 10.30am in summer on Tuesdays
at noon in the summer on 6 March
at dinnertime in 1990 on 25 Dec. 2010
at bedtime in the 1990s on National Day
at sunrise in the next century on Independence Day
at sunset in the Ice Age on my wedding day
at the moment in the past/future on New Year's Eve