The use of 'good evening'

:hi:
Hello,
I know 'good evening' is used as a greeting depending on the time the person is speaking.
BUT
I came across the use of 'good evening' at the end of a person's speech. (rather formal style)


My questions are:
Is it uniquely formal language?
Does the meaning remain exactly the same as the general one or is it slightly changed?
Maybe it is an old use?

Thank you in advance

If I hear 'good evening' as a parting words, I think it is both formal and rather dismissive.