Not saying this is anything, but maybe someone else on here will see this and have a lightbulb moment...
All 3 DNS records for Facebook, Whatsapp and Instagram were updated on Sep 22.
https://whois.domaintools.com/facebook.com
https://whois.domaintools.com/whatsapp.com
https://whois.domaintools.com/instagram.com
I also noticed the same date on the other domains:
https://whois.domaintools.com/whatsapp.net
https://whois.domaintools.com/facebook.net
I am sure there are others. This could be just a simple Zuckerberg and Co. had something they changed/updated on that date for the entire FB empire, but I find a massive outage a few days (12) later to be really strange.
I do not have a whois premium account so I am unable to dig much further than this. Anything interesting happen on Sep 22?
The "textbook" answer is 12-48hrs. In practice I have had Google domains DNS changes propagate within 30-90min. Non-Google ones can take a couple hours to a day, usually more in the couple hours zone.
DNS tripping out in minutes, simultaneously, worldwide DOES NOT HAPPEN.
Propagation is a global thing. You having it take 30 minutes where you live doesn’t mean the propagation finished, it just means it reached you, other parts of the country (and world) were likely still not updated. You have to use a DNS Checker to ensure the propagation has completed globally. In my experience we are still at the 12-24 hour mark for that