I think i found the bug in Firestorm: It's an issue with the Quick Preferences:
I always use the the dropdown menus in the quick preferences and it goes like this: SKY: Day cycle preset Water: Day cycle preset Day cycle: i click 'Shared environment' and it jumps to the SS ATMOS 6 or (something else)
If i click on the day cycle i made it also shows this day cycle in Day Cycle but still: The time is not right.
If i choose World -> Environment -> Use Shared Environment the field Day Cycle in the Quick Prefs menu shows none but finally: The day cycle works. Another Intersting fact is that if you choose daycycle: none in the Quick Prefs menu it does NOT work either because it jumps to SS ATMOS 6 again. The easiest way to get the parcel's daycycle is to click the big X right to the Personal Lightning button.
Thank you for your help!