I've been playing around with the challenge-tv demo dump lately, trying to rename the files (python scripting) according to date played. For MVD files there seem to be a matchkey included in the mvd files that consists of the recording date that can be used. For qwd and qwz files inside zip files i've managed to use the original modified date of the files inside the zip files to decide a somewhat somewhat correct date.

For qwd and qwz (and i guess .dem files even if they're not many) files that were never zipped however, is there a way to extract a date for those from the file itself by doing some special parsing?

I am pretty sure I have dump of the ch-tv database somewhere from 2005-2006'ish. Does it make sense to look for it and try to get it to work as a database again? It only does if uploaders were supposed to add the dates of the games. Were they?

Nope.
Only a very limited amount of client-important serverinfo data is stored in the dem/qwd files. I believe qizmo stuffs some message data at the beginning of the session into the header, but that has limited value, and I doubt it contains a date string.

I wrote scripts to parse the demos as well. This is the result: http://fpsplaybackdemos.netne.net/demosearch.php