After changing system time (e.g. going 5 months back and then going back to the current date triggers it in my case), the X timestamp is changed as well. This triggers e.g. KDE bug #90795 (http://bugs.kde.org/show_bug.cgi?id=90795). The best description of the timestamp I've found, in the glossary of the protocol specification, is a bit vague, but I think changing system time should not affect X timestamp. The X timestamp is no real time, and is used only to ensure ordering. Changing it when system time changes can e.g. make recent timestamps to become suddenly very old timestamp, thus breaking various things.
the X server has no way of knowing when the system time changes from under it. the timestamp is specified in milliseconds from server startup, and the only way to get that is to call gettimeofday(). gettimeofday() warps when you change the system clock. if you can come up with a portable way to calculate the time since server startup in milliseconds that doesn't warp when the system clock changes, that'd be great. until then this isn't fixable.
I disagree with the resolution "WONTFIX". This problem existed in the X server a long time ago, and was subsequently fixed in the XFree86 4.1.0 era by bug fixes to GetTimeInMillis(). Either the bug exists, can be verified by other people, and thus should be fixed, or it can not be verified, doesn't exist and then WONTFIX is a reasonable resolution. I don't see this as an unfixable problem. Reopening.
Actually, WONTFIX is not reasonable at all. If it isn't reproduceable then WORKSFORME is the appropriate resolution. I've seen various people report this problem via email lists and IRC however, so I'm inclined to think it's a real bug.
Created attachment 1027 [details] testapp showing current X time I used SUSE packages, but according to the packagers there shouldn't be any patch affecting this. This small testapp shows the current X timestamp. I tested a bit more with it, and it seems the problem exists only with large date changes. Going back or forth 2 minutes doesn't cause any problem.
Sorry about the phenomenal bug spam, guys. Adding xorg-team@ to the QA contact so bugs don't get lost in future.
we now use CLOCK_MONOTONIC where available, in xserver 1.3 and above.
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