Festivals are user-initiated events with beneficial effects. They are unlocked by researching Drama and Poetry from the Science tab.
Once unlocked, they can be found on the Village tab, under Management, below the "Send Hunters" button.
It costs 1500 catpower, 5000 culture, and 2500 parchment to initiate a festival.
Festivals last 400 days (one year). While the festival is ongoing, happiness is increased by 30% and and the kitten arrival rate is doubled.
Attempting to hold another festival while one is ongoing will set the remaining duration to 400 days, unless Carnivals have been researched, in which case it will add 400 days to the remaining duration.
If Numeromancy has been researched, festivals will give bonuses depending on the cycle.
All effects of festivals can be increased by running Breweries.