Incidentally, today is June 8th — my wife's birthday.
Literal
By-the-way today [topic-は] June 8th, wife [possessive-の] birthday [copula-です].
ちなみに 'by the way, incidentally' is a discourse marker introducing supplementary information. 妻 'wife' is the formal/humble word for one's own wife (as opposed to 奥さん for someone else's). A simple personal aside.