is this sentence grammatical?

[Englishlanguage]

Hello everybody,
I'd like to know whether the sentence below is grammatical.

I have had a perfectly wonderful evening, but this wasn't it

Thank you in advance

[Anglika]

It's fine.

[Englishlanguage]

It's fine.

Actually it's a quotation by an American comedian, thus it would have been pretty weird if it was ungrammatical.
Anyway, it doesn't sound good to my ears. What's does the last it refer to?

[Anglika]

The "perfectly wonderful evening" - which is not the evening on which he is speaking.

[Englishlanguage]

The "perfectly wonderful evening" - which is not the evening on which he is speaking.

Ok. I was just a bit counfused because I I heard this sentence from a friend of mine who doesn't speak English very well and it seemed he meant to say something else, but when I found out it was a quotation I realized that I was wrong. Anyway, thank you very much.
I just have one more question. Wouldn't simple past be more appropriate? Is present perfect used just to lead people to think he is referring to the evening of the day on which he pronounced the sentence and make a play on words since he soon states the contrary?

[Anglika]

That's it exactly!

He will get his laugh with the juxtaposition of "have had a perfectly wonderful evening" [then probably a slight pause] and "this was not it".

[Englishlanguage]

That's it exactly!

He will get his laugh with the juxtaposition of "have had a perfectly wonderful evening" [then probably a slight pause] and "this was not it".

Thank you Anglika...