Ivy Day -- when do the adcoms decide?

I am really curious about the timeline from now until announcements. When do admissions officers generally go into committee? Do the admissions make final decisions a couple of weeks before March 30 and are then busy with the bureacratic stuff? Or do they only finalize a couple of days ahead? Just wondering if someone had general insight – I imagine each school does it differently. Thanks!

The only person who could answer this would be an AO from one of the Ivies.