Thank you for you Reply!
Thats what I did to solve it:
I made a string variable as benchmark (WINTER), with every timestamp set to winter, then a months filter from March to October, where it checks if the variable is summer, if not it changes every string variable timestamp to one hour earlier, including the benchmark to summer. If its november it checks if the benchmark is winter. If not it forward shifts everything and so on. Maybe not the cleanest approach but its working.