"Scott Whitney" <swhitney@journyx.com> writes:
> Which I assume to be epoch dates and thusly converted.
This assumption is incorrect, which likely accounts for your confusion.
XID numbers have nothing to do with any external reality, and age()
results even less.
> If "today" is Saturday, a cronjob runs this command runs on each database:
> PGCMD = 'vacuumdb -f -v -z %s'
Seems like you should use the -a option instead of assuming that you
know which databases need to be vacuumed. You haven't shown us a
smoking gun here, but the failure to truncate pg_clog suggests that some
database is getting missed.
regards, tom lane