It is important that caches have the correct time - strange things can happen if they are set incorrectly! For example, whether a page is fetched from the target server or the cache depends upon the relative age of the files. If the cache's time is not correct then this calculation will give false results: in extreme cases resulting in files which have been changed on the target never being fetched.
When using AD authentication having the correct time (to within a few minutes) is essential: in this case if the time is out by more than a few minutes the connection between to Protex server and the Active Directory server will be lost and all internet access will fail.
This menu allows you to set up to four time servers: at least one should be the same time source your AD server uses: the AD server itself can act as an NTP server for your local network and this is the optimum situation.