Hello SimGuruFont. Thank you so much for you support. At least now we know the bug team gets aware of it.
@crin: The clock is not stuck at a certain time. It's more like a permanent hang. It begins with haning for 1 Sim-minute (so the clock skips every second minute). Then it gets worse by hanging 2 Sim-minutes and soon it hangs for several Sim-hours. Then the clock moves on to the actual time and hangs again immediately. All Sims are also stuck during that hang but the in-game time moves on as can be seen by the moving shadows, the moving sun and the moving star map. The needs of the Sims deplete while they are stuck.
I'm going to upload the save and I'll give you a note once it's done.
However it's from a custom world (Isabo Atoll).
@amjoie: We discussed that already in another thread and Sincerbox summed it up pretty good.