I didn't time or monitor the March 2025 release, but for February 2025, they released the availability calendar somewhere between 2:45AM-3AM PST. At least that is when I got the alert from rooms.aero. Kinda screwed me over since I was sleeping and didn't check until 8AM PST where half the calendar was already taken. So just be aware if you're based in the US and in PST/MST timezone.