Prepositions of time
He arrived _____ 9 o'clock _____ Thursday.
He arrived at 9 o'clock on Thursday.
What did you do _____ New Year's Eve?
What did you do on New Year's Eve?
My birthday is _____ summer. It's _____ July, _____ the 27th.
My birthday is in summer. It's in July, on the 27th.