[dns-operations] Storing Dates in DNS

[Crist Clark]

Looking for a standard or best practice for storing dates
and times in DNS, if such things exist. My Google-Fu is
failing me if such a thing is common knowledge.

More specifically, if there are accepted methods to store
the time a specific record was last changed within DNS.

If there is none, any suggestions smarter than an associated
TXT record with the Unix Epoch time would be appreciated.