Since you can load a database/log dump file into a different dataserver this would tend to rule out the backupserver pulling the details from a table. This means the dump times would need to be derivable from the dump file itself.
I'd suggest you take a look at the dump file metadata via the following 'with' options:
load { database | transaction } <dbname> from ... with { listonly | listonly=full | headeronly }
NOTE: When you include one of these 'with' options the 'load' won't actually occur; instead you'll receive a print out of the dump file's header/metadata.