http://www.bbc.co.uk/learningenglish/english/course/lower-intermediate/unit-3/session-2/activity-4

http://www.bbc.co.uk/learningenglish/english/course/intermediate/unit-25/session-2/activity-3

http://www.bbc.co.uk/learningenglish/english/course/upper-intermediate/unit-30/session-1

http://www.bbc.co.uk/learningenglish/english/course/towards-advanced/unit-4/session-1

• at
  • specific times on the clock
  • mealtimes and specific points of the day
  • specific points of the week
  • special celebrations
• on
  • specific dates
  • specific days
  • days of the week
• in
  • specific parts of the day
  • months
  • seasons
  • years and centuries

https://learnenglish.britishcouncil.org/en/english-grammar/adverbials/adverbials-time/time-and-dates http://dictionary.cambridge.org/grammar/british-grammar/at-on-and-in-time

http://www.bbc.co.uk/learningenglish/english/course/intermediate/unit-2/session-1