It's random.
In Europe the first one was from 9-15, the next one 18 hours later from 3-9 and then the one after that was 19 hours later from 22-4. People expected it at 21, but it wasn't. It's random. Just because you see a pattern now doesn't mean there is on. If you roll a die several times and you get a 1, then a 2, then a 3, it doesn't mean that the next thing you're gonna roll is gonna be a 4. If you consecutively roll three 6s, that doesn't mean that you have a die that always rolls a 6.