This guide gives a schedule for the end of wars.
All wars last up to three days. They end at midnight (UTC).

Four factions fight over five planets in a single war.
A faction can have up to 20 members.
Multiple wars will be going on at the same time.
Once you join a faction, you cannot join a new faction until that war is over.

Depending on when you join a faction, the difficulty of war and the difficulty of joining the same faction as your friends will change.
It will be difficult right after the war is over.
This is because there will be a rush of many aggressive players who want to hold the planets for a long time and earn a lot of favors.
Therefore, plan when to join factions.

Note: This schedule was checked in version 2.0.1. It may change in future updates.