I know we can negate place, manner, etc. by just placing a 不 before the verbs (prepositions) that introduce the clauses.
But how can I negate time, since it doesn't have a verb/preposition before it?
For example: I wake up not at 8am, but at 9am.
Would I have to place a 在 before the time?
Would this be the only mandatory 在 when we talk about time or are there other situations it's required?
Thank you for any help!