Italy is one hour ahead of Greenwich Mean Time (GMT).
The time difference between Italy and some major cities is as follows:

London: -1 hour
New York: -6 hours
Chicago: -7 hours
Denver: -8 hours
San Francisco: -9 hours

When first arriving in Italy, this can have a dramatic impact on a traveler as jet-lag hits and your body tries to adjust to the sun being up 2 or 3 hours after you are used to going to bed. Daylight savings time is observed from the end of March to the end of October.