I'm running into this same problem, however I'm unable to change the forum time zone.  So this is going to be a really stupid question.  According to www.dotnetnuke.com/Resources/Knowledge/DotNetNukeOnlineHelp/DotNetNukeOnlineHelpVersion46/tabid/1157/TID/1954/Default.aspx it says to change the timezone settings by clicking on the Admin button >> Click on General Settings.  It then says on step 3h) "At TimeZone, select the time zone to be used for this forum from the drop down list."  However this setting does not exist on my forum installation, nor does it exist in the database.  The screen shot referenced on the ink above, have the same available settings as in my forum.  As you see, there's no timezone dropdown listed.

We're using forum version 4.4.3, any assistance would be most appreciated.

Matthias,

Thanks for your reply.  I double checked all the settings and this is what I came up with:

Portal Timezone = (UTC -7:00) Mountain Time (US & Canada)
web.config = <globalization culture="en-US" uiCulture="en: .../>
Server Timezone = (UTC -7:00) Mountain Time (US & Canada)

For some reason when we post on the forums it sets the time 7 hours ahead [(UTC 0:00) Dublin, Edinburgh, Lisbon, London]. Is there any other place we should be looking?