There are different prepositions that we can use to talk about time:
at:
exact time (at 10 o'clock),
meal times (at dinner time),
poins of time (at noon, at dawn),
festivals (at Christmas),
age (at (the age of) 13)
on:
days of the week (on Friday),
parts of the day (on Monday morning),
dates (on 31 December),
festivals (on New Year's Eve),
anniversaries (on your birthday)
in:
parts of the day (in the afternoon),
months (in August),
years (in 1492),
seasons (in (the) summer),
centuries (in the 20th century),
festivals (in Easter week),
periods of time (in the holidays)
For more practice, watch this video: