StarTeam has a personal option called 'use last modified time for checked-out files’. This setting has a direct influence on the file time stamp applied to the files on disk,

This setting is accessed on the menu TOOLS | PERSONAL OPTIONS | FILE - checkout

If the option is unchecked then when a file is checked out, the file modified time is set to the ‘current time’ on the local machine.

If the option is checked, then when a file is checked out, the file modified time is set to the value of the CONTENT_MODIFIED_TIME (“Modified”) property for the checked out revision. So it is the ‘Modified Time’ whose value is used, not the ‘file timestamp at checkin’

The file timestamp at checkin is different from the modified time. File timestamp at checkin is the value of the file time on disk when the file was checked in.