Every community day never fails to impress me. Hold your high quality bait pokemon months ahead.
Happened midway through Community Day. I prepare high quality bait pokemon several months ahead for a very good reason.
If you have to make events like this please upgrade your servers Niantic or it's literally not going anywhere. Monthly occurences like this is blatantly and perfectly inexcusable.
EDIT: Everything is back to normal for now but it's unsettling that this appears every month.
EDIT: Community day CANCELLED. Yes, you read it right. Death in its finest form.
TL;DR: Massive server errors happen every community day. Prepare high iv egg hatches and wild catches to prevent absolute disaster. I am least affected since i already had multiple reserves for this one.

Answers
Even I'll admit that the number of times the Asia Pacific Region gets screwed over by network errors during CD events is pretty appalling. Has there ever been a CD where things have gone smoothly for trainers who play in that region?
That said, Niantic will probably reschedule Beldum CD for any areas where the event was cancelled. They did something similar for Articuno Day, so I'd like to think they would do the same in this instance as well.