REVISION: Prepositions of Time (at - in - on)

Some explanations:

http://www.english-4u.de/prepositionoftime.htm (focus on AT - IN - ON)

http://www.englisch-hilfen.de/en/grammar/preposition_time.htm   (focus on AT - IN - ON)

Activities:

http://www.perfect-english-grammar.com/time-prepositions-exercise-2.html

http://www.agendaweb.org/grammar/prepositions-of-time-exercises.html