For a very formal wedding, men should wear morning suits if it is in
the daytime, and white tie if it is in the evening. If it is less
formal, men may wear strollers in the daytime and tuxedos in the
evening. For even less formal weddings, men may wear ordinary suits
at any time of day. To be technically proper, men should never wear
tuxedos in the daytime or morning dress in the evening.

That said, many people ignore these traditional dress guidelines, and
wear tuxedos in the daytime.

Other faq about getting married in Italy