'He is in Italy for a month' implies that he is there for a period of one
month, which is not yet over. It doesn't tell us when he arrived.
'He has been in Italy for a month' means that he arrived in Italy a month
ago. It says nothing about how long he will continue to be there.
https://forum.wordreference.com/threads/he-is-has-been-in-italy-for-a-month.4048038/