Prepositions of Time - Preposições de Tempo

at        in       on
PRECISE TIME        MONTHS, YEARS, CENTURIES and LONG PERIODS         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 Christmas Day
at sunrise        in the next century      on Independence Day
at sunset        in the Ice Age      on my birthday
at the moment        in the past/future      on New Year's Eve