Like other European countries, in Italy we use the 24 hour system when referring to official hours like office hours, opening and closing hours, etc.
At the same time, in informal settings, it is way more common to use the 12 hours system by specifying the part of the day — di mattina(in the morning), di pomeriggio(in the afternoon), di sera(in the evening), di notte(at night) — when it is useful to avoid possible confusion.