If The Timestamp displayed in the Administrator GUI and the logs is different from the system timestamp, Adding the below property in the TIBCOAdmin_<domain>.tra file under <TIBCO _HOME>administrator/domain/<domain name>/bin folder should force the JVM to use the correct time.
java.property.user.timezone=<desired time zone>

Add the above property and restart the domain Administrator service.

example:

java.property.user.timezone=US/Eastern

Note: If the changes are being made on a windows machine, update the TIBCO administrator NT service before restarting.