Determining when sys db changed occurred

mgti-noc of course, you can see it in Audit logs in CLI and GUI also as below

from CLI :-

tail /var/log/audit | grep 'db_variable'

From GUI:-

System >> Log >> Audit : List

mgti-noc This should appear in your logs but I can't remember if it's in the audit or ltm log. If you have a syslog server that collects this data you should be able to go through those logs and see exactly when it was changed.