Most Italians take a two week vacation (called Ferragosto on August 15th) either before or after August 15th. Most large industries are closed during August and many museums and restaurants might also be closed. Many people take the entire month to rest and relax before returning to work and school on September 4th.
The other period of time when holidays might affect normal business hours is the period between Christmas, New Year's Day and the Epiphany on January 6. Since Italy is a Catholic country, many national holidays coincide with religious holidays.
In addition, all Italian cities celebrate the patron saint as a legal holiday. All businesses are closed on...