I just got an email: Happy hour is:
For a whole month, from 28/01 to 01/03, every day between 5pm and 9pm (GMT +1:00), it’s Happy Hour on Urban Rivals. Load up on Clintz for an hour.
1 damage = 1 Clintz.
Just turn up in any room (except the Training, Guild and Events rooms) and get playing! Don't hang around. Make the most of it.
So, except Survivor and ELO, best case scenario would be 11 damage (Unfuried Kolos/General Cr etc with Timber) + 13 damage (Furied Kolos/General Cr etc. with Timber) for a total of 24 damage/match which equals 24 clintz. For an average of 3 minutes per match, that would be around 480 clintz an hour times 4 hours equals 1920 clintz.
I would say that about 800-1000 clintz per day would be a more realistic scenario and a more than optimistic one so meh... not that impressed honestly.
If I understood it wrong and you can only get this bonus for one hour in that timeframe of 4 hours, then this is rubbish...