Well, it needs to be dark out. 8pm is dusk in a lot of places so that’s out. 9pm could work but it’s got the same issues that you list. 10pm for a lot of people is after they put kids to bed.

One of the points of this effort is to make it accessible to everyone. Literally you can step outside and just hold up your phone light. If you’re rural and gather 10 people and call the local news, maybe they’ll see you. If you’re in a big suburban sprawl area, you can join people in a park or in the nearest city center and be seen. Have you seen the pictures from Serbia’s 15th for 15? It’s powerful. Their PM literally submitted his formal resignation right after.