Enjoy the longest evening of the year at Uetliberg.
We will leave Zurich Triemli TRAIN station at 19:00 (not Triemliplatz). The hike will be 1 hour 30 minutes taking route 47. See link. We get to the top, we relax, we eat some snacks, we have a long drink, and we watch the sun set on Zurich ~ 21:26. The S10 train will take us down a little past 22:00.
I think the forecast for clouds that night is wrong also.