The Fesitval of Dionysus
This festival is always held between the last day of Octembus and the first day of Novembus (and so can, in effect, be considered the 26th of Octemnbus).
The Church of the Twelve has denoted that this day be a festival of happiness, and even excess, as a 'reward' for all of the hard work ensuring another successful harvest and it has long been one of the most popular festivals in the calendar. For workers it is a mandatory time to relax, for businesses it is a time to get rid of old wine and beer stock before the winter and for petty thieves it's a time to take advantage of the many, many drunk citizens in the towns and cities of the Empire.
The big problems with this festival are as follows:
1. Not everyone follows the Twelve and so their beliefs need to be catered for
2. The amount of minor vandalism that occurs is expensive for towns and cities to repair
3. The city and town watches usually can't cope with the increase in crime during the festival