In April 1900, Professor L. A. Grosclaude of Geneva proposed the Invariable Calendar, New Era Calendar, or Normal Calendar with 12 months and four 91-day quarters of exactly 13 weeks. The final month of each quarter would have 31 days, the others 30 days each. Quarters all began on a Monday. An additional day, termed New Year's Day, that was not any day of the week and not part of any month, would occur between December 31 and January 1. Another such day is inserted between June 31 and July 1 on leap years. This placement of the leap day is virtually the only difference to Armelin's calendar which has it at the end of the year. This model would be a

perennial calendar A perennial calendar is a calendar that applies to any year, keeping the same dates, weekdays and other features. Perennial calendar systems differ from most widely used calendars which are annual calendars. Annual calendars include features par ...

, with each date occurring perennially on the same day of the week. Grosclaude lists many business advantages to this. Three monthly days important to businesses, the 1st, 15th, and 30th would always occur on the same 3 days of the week, respectively, and additionally would never occur on a Sunday, for example. It became the model for

The World Calendar The World Calendar is a proposed reform of the Gregorian calendar created by Elisabeth Achelis of Brooklyn, New York in 1930. Features The World Calendar is a 12-month, perennial calendar with equal quarters. Each quarter begins on a Sunday ...

, promoted by Elisabeth Acheils and The World Calendar Association since 1930.

Structure

{, class="wikitable" , + Quarter layout by weeks ! Q1 month !! Q2 month !! Q3 month !! Q4 month ! Mon !! Tue !! Wed !! Thu !! Fri !! Sat !! Sun , - !rowspan=5, January !!rowspan=5, April !!rowspan=5, July !!rowspan=5, October , 01, , 02, , 03, , 04, , 05, , 06, , 07 , - , 08, , 09, , 10, , 11, , 12, , 13, , 14 , - , 15, , 16, , 17, , 18, , 19, , 20, , 21 , - , 22, , 23, , 24, , 25, , 26, , 27, , 28 , - , 29, , 30, , colspan=5 , - !rowspan=5, February !!rowspan=5, May !!rowspan=5, August !!rowspan=5, November , colspan=2 , , 01, , 02, , 03, , 04, , 05 , - , 06, , 07, , 08, , 09, , 10, , 11, , 12 , - , 13, , 14, , 15, , 16, , 17, , 18, , 19 , - , 20, , 21, , 22, , 23, , 24, , 25, , 26 , - , 27, , 28, , 29, , 30, , colspan=3 , - !rowspan=5, March !!rowspan=5, June !!rowspan=5, September !!rowspan=5, December , colspan=4 {{n/a, , 01, , 02, , 03 , - , 04, , 05, , 06, , 07, , 08, , 09, , 10 , - , 11, , 12, , 13, , 14, , 15, , 16, , 17 , - , 18, , 19, , 20, , 21, , 22, , 23, , 24 , - , 25, , 26, , 27, , 28, , 29, , 30, , 31

Criticism

* The

Sabbatarian Sabbatarianism advocates the observation of the Sabbath in Christianity, in keeping with the Ten Commandments. The observance of Sunday as a day of worship and rest is a form of first-day Sabbatarianism, a view which was historically heralded ...

objection, that the strict cycle of the seven-day week is interrupted; sometimes there are seven days between sabbaths, instead of the usual six. * Difficulties of defining the dates of New Year's and Leap Days when they don't belong to any month or week.

Other calendars and proposals

* List of calendars: Reform calendars * Calendar reform: Specific proposals * Armelin's calendar

Sources

A Proposed Plan For An Invariable Calendar
Sunday Magazine, David Friedman, June 25, 2010 at 9:02 am
PDF

June 26, 1910, The New York Times, Hedley P. Somner
PDF

The Reform of the Calendar
Popular Astronomy, vol. 20, pp. 232–236, 04/1912, Ralph E. Wilson
PDF
*
The Reform of the Calendar
Publications of the Astronomical Society of the Pacific, Vol. 24, No. 141, p. 113
PDF

Wanted—A Brand-New Calendar
Popular Science, Jan 1927, pp. 33–34, 134-135, Frank Parker Stockbridge
THE REFORM OF THE CALENDAR
ALEXANDER PHILIP, 1914
DiagramPDF
Proposed calendars