Hi JL
Read the below document and follow the same to make the changes to time stamp.
It clearly explains how to change BWOM_SETTINGS and which datasources are all affected and what does all the field means. It would easily allow you to get what you need.
But be careful in changing the setting since this might affect other datasources as well. Try in test system and then implement in production system.
http://scn.sap.com/docs/DOC-39843
Hope this helps
Regards
Karthik