Linode DNS propagation time
The DNS propagation time for our name servers is 30 minutes. The timing could vary up to 48 hours to propagate across the entire web. A way you can diagnose if this is a DNS caching issue or misconfiguration is by running dig with the following option.
$ dig +trace www.yourdomain.com
Linode Support Team
Thanks for the update.
The linode DNS dashboard has the line "Changes made to a master zone will take effect in our nameservers every quarter hour.", so, I was under the impression that any changes will be visible after 15 minutes at max. Is there another point of delay in the system that's adding the other 15 minutes?