I have made up the examples below.
(1a) My appointment is at 2:30pm.
(1b) My appointment is 2:30pm.
(2a) My appointment is on April 4th.
(2b) My appointment is April 4th.
Do I need the prepositions? Thank you very much for your time and help.
They are all OK, but 1A and 2A are a little more standard.
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