how can you set the effective period in the scene so that the action is performed from sunset to sunrise?
currently it is possible to enter only a fixed time interval and not variable with night and day.
Thanks
? Under scenes is Sunrise/ Sunset.
Please explain further. 
From sunset to sunrise. Not sunrise or sunset in effective period camp
The Ewelink App will support sunrise and sunset in the September release, so let’s wait patiently together.
While we wait patiently fro September with @songal - I use a bypass trick for now. I have an existing auto scene that controls some lights sunset to sunrise. I wanted to control some other device, but it must work only between sunset and sunrise… So I set up the new scene IF scenario to say “if all conditions met” and I included the lights device “on”.
But I agree, it will be nice to see sunset / sunrise in the effective period 
thanks Pierre, a great workaround.