You can’t switch DNS entries on & off at will and expect them to be accurate across the globe so quickly. The issue is that DNS entries are basically huge databases of information that only get changed & synced on a schedule that is pretty much out of your control. To sum up:
When you make a DNS change on your side there is absolutely, positively no assurance of how long it will take that change to propagate across the Internet.
That said, there are ways you can smooth the process. And that is by controlling the TTL (Time-To-Live) of your DNS entry. This is the time (in seconds) that tells other DNS servers when to refresh the status of entries.
By default, the TTL of a DNS entry will be 86400 seconds. Which is equal to 24 hours. This is pretty much the globally agreed upon default setting for DNS entries. Meaning, everyone in the world pretty much agrees to update a DNS entry info after 24 hours.
But that said, like people, each server & service is set differently. Some will take exactly 24 hours. Some will take longer. At the end of the day, it’s not in your control so you must allocation 24 to 48 hours for changes to happen.
So I said “there are ways you can smooth the process” and here is what you can do. Most hosts & DNS registrars will allow you to adjust the TTL for a hostname. The the fastest one can speed up DNS TTL is to set it to 300 seconds (aka: 5 minutes). It’s pretty much an agreed on standard that while 24 hours is acceptable for established hostnames, 5 minutes is an acceptable speedup for switching IP addresses on a temporary basis.
I emphasize, temporary because—like explained before—the established & agreed upon standard for updating info for hostname records is 24 hours. You can’t suddenly keep your TTL to 5 minutes and expect people to have their servers pay attention. Many admins actually do not consider requests for TTL to be 5 minutes a serious thing & will simply force DNS refresh after 24 hours no matter what you set.
But setting the TTL 300 seconds in a short window of time before an IP changes, and then keeping it in place for 24 hours after the IP change happens can help you speed up the process for the majority of DNS servers out there. Far better than leaving the TTL to 86400 seconds.