Battle day does not necessarily needs to take 24 hours to end. As long as both clans finish all the attacks, there is no reason to wait until the end of the day.
This would solve two issues:
1 - People complaining (and suggesting) for shorter battle days, because considering that it takes almost 1 hour to find another clan, wars always starts each time later
2 - The last hours when everybody has already attacked are useless



