I have a Mediawiki installation that I installed as a One Click Install. It’s working fine except that on most pages it is giving out a Last-modified: header of “Thu, 01 Jan 1970 00:00:00 GMT”. This is obviously not right. I’ve checked the Mediawiki code and it doesn’t appear to be setting that header at all. What else could be doing it?
If you’re dealing with caching issues, see this excellent info on disabling caching in Mediawiki. I don’t see why it’s enabled in the first place.
I had this problem as well, after searching the internet to no avail I discovered what was causing it for me. I’m running Mediawiki 1.6.10 for reference, an older version for php compatibility reasons. Anyways the problem was that the character limit for the revision date in the MYSQL database was too small for the timestamp. Instead of being 14 characters limited it was set to 4 for some reason. In your SQL db for your wiki look for the table called yourdbprefix_revision in that table find the column rev_timestamp and check its datatype, if it’s set to anything less then VarChar(14) change it and save the changes. Now when you edit a page the revision will show the correct date.