The Dove Calendar is a simple calendar, devised by Karl Palmen, where the days are grouped into consecutive periods of seventeen days called doves.
Years alternate between 21 and 22 doves (357 and 374 days) for 33 years beginning and ending with a short year of 21 doves. This gives rise to a mean year of 365.242424.. days.
The doves are named with capital letters A to U or V and the days of the are named with small letters a to q, so for example new year's day is Aa. The new year is chosen such that March 20 of the Dee-Cecil calendar always occurs in the last dove of a year. The current 33-year cycle began on 29 March 2013.
See The Dove Calendar for more details.