At least from the online resource I found:
Carnival, February 28th
Formerly a wake for an old age and a birthday party for a new one, Carnival has risen in prominence since High King David assumed the throne. Now it celebrates the new unity between nobles and commoners. It is a night when kings and queens enchant entire cities, enabling the wholesale gathering of Glamour. Masked by the human Mardi Gras festivities, Carnival celebrations mark some of the Kithain's wildest parties.
Borrowing from such diverse sources as English Boxing Day and the ancient festival of Lughnasa, the ritual central to Carnival involves the elevation of a local mortal, befuddled by alcohol or dizzy with an overdose of Glamour, to the position of King or Queen of Carnival, while the local monarch takes the part of a jester. The new "monarch's" word is considered law, although in most cases, the chosen mortal is too addled by the effects of substance abuse to issue any commands which might have lasting repercussions. The "jester," on the other hand, is open to all the abuse of his or her new position. Some kings and queens dread the approach of Carnival, but put up with it as part of their duty as rulers.
There are only three laws of Carnival:
* There can be no retribution for any word spoken or deed done. A monarch cannot exact revenge against harassers.
* Carnival is sacrosanct; all who attend are welcome and safe. Anyone violating this principal is summarily subjected to any punishment decreed by the bleary-eyed Carnival King or Queen.
* Let merriment reign!
Carnival ends at sunrise on the following day. In most cases, the Carnival King or Queen is released from duty and sent home, none the worse for wear. In certain Unseelie demesnes, it is rumored, the mortal becomes a ritual sacrifice.