Wrong timezone on PC seems to set zimbraPrefTimeZoneId - followup
The resetting of the timezone is not permanent - the next time a user accesses Zimbra from certain PCs the TZ is changed back to GMT-08.00.
I thought that the problem was from external PCs with the TZ set incorrectly (ie: to GMT-08.00) but this is not the case.
It seems that all the PCs in the internal LAN (a 192.168.x.x subnet) cause the TZ to be reset to GMT-08.00 as soon as the user logs on to Zimbra - this happens with IE and Firefox. All the PCs have their TZ set to AEST (GMT+10.00) according to Control Panel's 'Date & Time' applet - so I am perplexed as to what setting on these PCs causes Zimbra to change its TZ.
Logging onto Zimbra from an external PC (also with the TZ set to GMT+10.00) will case the Zimbra TZ to be changed to GMT+10.00
The internal PCs access the Zimbra PC directly and not through a proxy, they all run Windows XP with roaming profiles and are part of a Windows 2003 AD domain.
So how does Zimbra determine the TZ of the client?