the same number of business days, and that each day falls on the same day of the week each year. The day of the week on which each month starts can be memorized. Thanksgiving Day falls always on November 30. A major disadvantage is for sabbatarians, who are obliged to worship every seventh day. Their holy day will occur on a different weekday every year. Armelin's project received the first premium of the French Astronomical Society. The World Calendar, roughly identical, has been promoted by the World Calendar Association since 1930. See also Invariable Calendar References Proposed calendars