Leap week calendar week calendars would synchronize with the Gregorian every 400 years Note that the new years of the calendars shown need not be synchronised. The years according to ISO week date applied to months, i.e. a month has as many weeks as it has Thursdays, are shown depending on the weekday of 1 January, shaded weeks belong to the month they are labeled with in regular years and to the other adjoining one in leap years. Leap week calendar A leap week calendar is a calendar system with a whole number of weeks every year, and with every year starting on
Armelin's calendar mind of modest ability will learn in a few minutes the weekday with which each month invariably begins, and will be able to compute quickly the day of the week upon which any day of any month falls. Each stated holiday falls upon its invariable day of the week. 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