DayZ forces an incorrect refresh rate (144 Hz, which is maximal refresh rate supported by my display) instead of the desired 120 Hz (which I desire to use and is configured for the desktop (and used in any other application as well)).
Using
refresh=120;
in DayZ.cfg does not resolve the issue as it appears to be ignored. Deleting the config has no impact on the issue.
This issue appears to be independent of both the Windows version and GPU manufacturer, for I have observed it on the current iterations of Win 8.1 Pro (HD5850, current Crimson Legacy driver) as well as on Win 10 Pro x64 (nvidia GeForce GTX 970, 368.81). In the nvidia control panel, the option "Preferred refresh rate" is set to "application-controlled" for obvious reasons.
Addendum: The issue might be related to Alt-Tabbing. I've seen it start in 120 Hz just fine, but after Alt-Tabbing out and back in it ran in 144 Hz. After shutting it down it keeps starting in 144 Hz, even after a reboot. I have not yet figured out what resets the cycle; there might be something else involved.