The DOE has their high school admissions events calendar back on their website:
You need to scroll down a bit to find it.
In past it was both helpful and incomplete. I saw things posted that I didn’t see anywhere else, but less than half the open houses/tours going on in the city made it onto this calendar. The onus was on individual schools to share their info and that didn’t seem to happen on a consistent basis. But, perhaps they’ve got a better plan for keeping this up to date and comprehensive this go round.