Milan is 5 hours behind Jakarta
Best overlap: 1:00 PM to 6:00 PM in Jakarta is 8:00 AM to 1:00 PM in Milan.
If you set up a recurring sync, 1:00 PM to 6:00 PM in Jakarta (8:00 AM to 1:00 PM in Milan) is the natural home for it. Around 5 hours of overlap is enough to work comfortably, as long as meetings don't drift to the end of one team's day. Finally, Milan observes daylight saving and Jakarta doesn't, so this window shifts by an hour for part of the year — recheck it each spring and autumn.