Leap week calendar

From Wikipedia, the free encyclopedia

A leap week calendar is a calendar system with a whole number of weeks every year, and with every year starting on the same weekday. Most leap week calendars are proposed reforms to the civil calendar, but some - such as the ISO week number calendar - are simply conveniences for specific purposes.

The ISO calendar in question is a variation of the Gregorian calendar that is used (mainly) in government and business for fiscal years, as well as in timekeeping. In this system a year (ISO year) has 52 or 53 full weeks (364 or 371 days).

Leap week calendars vary on whether the concept of month is preserved and whether the month (if preserved) has a whole number of weeks.

Most leap week calendars take advantage of the fact that 400 Gregorian Calendar years have exactly 20,871 weeks, so with non-leap years of 52 weeks, this means there are 71 leap weeks every 400 years. These include the Pax Calendar, CCC&T as well as the ISO week dates.

Contents 1 Advantages 2 Disadvantages 3 Year structures 4 External links

[edit] Advantages

• There are no variations between day of week between years for a specific date.
• The calendar starts on the same day and week every year.
• Unlike the regular calendar, variations of years are limited to a possible addition of a leap week.
• There are no fragments of weeks at the end of the year.
• Unlike certain proposed calendar reforms such as the World Calendar and International Fixed Calendar, there is no need to modify the week. This avoids opposition from religious groups who object to interruption of the seven-weekday sequence.

[edit] Disadvantages

A year with a leap week is at least 7 days longer than a year without a leap week, consequently the equinoxes and solstices must vary over 7 days, (i.e. ±3 of the average date), or even more, such as 19 days in the Pax Calendar.

[edit] Year structures

Calendars with leap week at the end

ISO week	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							32							33							34							35							36							37							38							39							40							41							42							43							44							45							46							47							48							49							50							51							52							53
Day
13 months	1																												2																												3																												4																												5																												6																												7																												8																												9																												10																												11																												12																												13																												*
Bonavian	1																																			2																												3																												4																																			5																												6																												7																																			8																												9																												10																																			11																												12																												*
Sym454	1																												2																																			3																												4																												5																																			6																												7																												8																																			9																												10																												11																																			12																												*
30-31-30	1																														2																															3																														4																														5																															6																														7																														8																															9																														10																														11																															12																														*
Gregorian	January																															February																												March																															April																														May																															June																														July																															August																															September																														October																															November																														December																														*
Quarter	1																																																																2																																																																3																																																																4

Note that the new years of the calendars shown need not be synchonised.

[edit] External links

• Leap Week Calendars
• List of ISO leap years - here the leap weeks are called Newton