Originally Posted by Kranebitten

The current Ministry of Health rules in general for entry into Italy run out on the 30th of July (including the additions for the UK). Expect them to be extended/updated shortly, though the main focus in Italy in the last few days has been on the broader set of national Covid rules coming into force in August.

As others have said the Italian rules are sample for your PCR/Antigen test taken within the 48 hours before arrival in Italy, the current 5 day quarantine starts from the next day (like in UK arrival day is day zero). You also have to test at the end of day 5 and should reach out to the local health service for your region to advise them when you are at the address you are doing your quarantine in and they will sort your day 5 test for you and advise where to go for it.