I have not tested this in SH5, but I do know that in SH4 and SH3 that the "time of day" is tied to the graphics card and a 30fps factor through the DirectX v9.0c dll interface. What can happen in 4 & 3 is that the newer computers, with higher possible framerates with the newer video cards and displays can get over 100+fps rather easily, which will then make the DirectX dll library run 3 or more times faster than desired. Front Runner did a study in SH4 about this, in conjunction with his "Base Time 2018" thread, and shows his set-up for a 144Hz display in
Interesting new issue regarding sync rate - it took a lot of experimenting for him, since he does 1x TC almost exclusively. A couple of posts above that is his "conventional" set-up. If you have ATI/AMD graphics, rumor has it that they have a similar function in their driver front-end.
A ~REALLY~ big contributor to the issue though, even if you have everything configured "correctly" (what, after all, is the definition of "correctly" in a Silent Hunter game???), is shelling-out to Windows, whether intentional, for using external tools with the game, or accidentally when a Windows 'background' process pops to the fore. You would usually have other graphics anomalies, and maybe even Sound issues. Those generally, in SH3 & 4 anyway, 'correct' themselves with a Save, exit of the game, re-start the game, and then a Load of the Save game. You do have to exit the game in SH4 for those issues to "re-set"... I cannot remember about SH3 in that regard, and I have never had the issue in SH5... YMMV, and experimentation or the name of the game.
btw, I really appreciate your patrol reports Markus Witt. Excellent reading, and ~very~ authentic looking. Cool beans!