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Leap week calendar

From Wikipedia, the free encyclopedia

A leap week calendar is a calendar system with a whole number of weeks in a year, and with every year starting on the same weekday. Most leap week calendars are proposed reforms to the civil calendar, in order to achieve a perennial calendar. Some, however, such as the ISO week date calendar, are simply conveniences for specific purposes.[1]

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. The Pax Calendar and Hanke–Henry Permanent Calendar preserve or modify the Gregorian month structure. The ISO week date is an example of a leap week calendar that eliminate the month.

A leap week calendar can take advantage of the 400-year cycle of the Gregorian calendar, as it has exactly 20,871 weeks: with 329 common years of 52 weeks plus 71 leap years of 53 weeks, a leap week calendar would synchronize with the Gregorian every 400 years since (329 × 52 + 71 × 53 = 20,871).

YouTube Encyclopedic

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  • Why Does February Only Have 28 Days?
  • What Is a Leap Year?

Transcription

[MUSIC] Although February 2015 might fit perfectly on the page, every year it’s the runt of the monthly litter. This deficit of days, this calendar craziness, this oddity of the annum, like so much of modern culture, is the Romans’ fault. Here’s the crazy story of why February has 28 days… except when it doesn’t. [MUSIC] Romulus, the maybe-mythical, maybe-real founder and first king of Rome, had a problem. With an increasing number of festivals, feasts, military ceremonies, and religious celebrations to keep track of, Romans needed a calendar to organize all of them. Ancient astronomers already had accurate calculations for the time between two solar equinoxes or solstices, but nature had given people a nice, easy pie chart in the sky to track the passage of time, so early Rome, like many other cultures, worked off a lunar calendar. The calendar of the Romulan republic had ten months of either 30 or 31 days, beginning in March and ending in December, and we can still see traces of that calendar today. Problem was, that year was a few days short of four seasons. Romans were too busy not dying during winter to count those 61 and a quarter extra days… they’d just start the next year on the new moon before the spring equinox. It’s actually not a bad system, as long as you don’t have to figure out what day it is between December and March. So the second king of Rome, Numa Pompilius, tried something else. Even numbers were bad luck in Ancient Rome, so Numa started by removing a day from all the even-numbered months. And being loony for Luna, Numa wanted his calendar to cover 12 cycles of the moon, but that would have been an even number, so he rounded his year up to 355. Numa split the remaining days into two months and tacked them on to the end of the year. And that’s how February got 28 days. Yes, it’s an even number, but since the month was dedicated to spiritual purification, Romans let that one slide. But, as powerful as Rome may have been, they couldn’t change the rules of the universe, and neither of these calendars add up anywhere close to the time it takes us to orbit the sun. After a few years, the seasons are out of whack with the months, dogs and cats, living together, mass hysteria!! Did we already use that joke? This is where it gets even weirder. See, February was actually split in two parts. The first 23 days and… the rest. Every year, Numa’s superstitious calendar would be out of line with the seasons by a little more than 10 days. So every other year, the last few days of February were ignored and a 27-day leap month was added after February 23rd or 24th. This way every four years would average out to 366 and a quarter days… which is still too many days, but hey, we’re getting there. Confused? You should be. Numa! This system could have worked, every 19 years, lunar and solar calendars tend to line up, so add enough leap months to keep the seasons in order and eventually everything will reset itself. Except these leap months weren’t always added according to plan. Politicians would ask for leap months to extend their terms, or “forget” them to get their opponents out of office. And if Rome was at war, sometimes the leap month would be forgotten for years, and by the time Julius Caesar came to power, things had gotten pretty confusing. Caesar had spent a lot of time in Egypt, where 365-day calendars were all the rage, so in 46 BC, he flushed Rome’s lunar calendar down the aqueduct and installed a solar calendar. January and February had already been moved to the beginning of the year, and Caesar added 10 days to different months to get a total of 365. And since a tropical year is a tad longer than 365 days, Julius added a leap day every four years, except they inserted it after February 23, right in the middle of the month. Apparently February is the trash heap of the calendar, just do whatever feels good. For all their work to reform the calendar and other stuff they did, the 7th and 8th months of the year were renamed for Julius and his successor Augustus Caesar, despite the fact that Pope Gregory would have to adjust it again in 1500 years. But that’s a story for a different day. Or month. I don’t even know anymore. Stay curious.

Advantages

  • The calendar starts on the same day of the week every year; there are no fragments of weeks at the beginning or end of the year.
  • Unlike the Gregorian Calendar, variations of years are limited to the possible addition of a leap week.
  • Unlike certain proposed calendar reforms such as the World Calendar and International Fixed Calendar, there are no exceptions to the 7 day cycle of the week. This avoids opposition from religious groups who object to the interruption of the weekday sequence.

Disadvantages

  • Although the calendar starts on the same day of the week every year, not all countries observe the same day as the start of their week. This will therefore present an issue if a leap week calendar is intended for use in multiple countries.
  • A year with an intercalary/leap week is 7 days longer than a year without an intercalary 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.
  • While persons born during the added intercalary week lose their real birthday in common years, similarly to those born on 29 February in the Gregorian calendar, approximately 1 in 294 days would belong to an intercalary week, compared to the approximately 1 in 1506 days that occur on 29 February.
  • Leap year rules are more complicated than the Gregorian, since leap years are not at fixed intervals, meaning there is no simple approximation (i.e. one in four years): see Pax Calendar and Hanke–Henry Permanent Calendar § Disadvantages and Symmetry454 § Leap rule. The best comparable rule to Gregorian "every fourth year, except when divisible by 100, unless also divisible by 400" probably is "every fifth year, except when divisible by 40, unless also divisible by 400", at the expense of even more severe astronomic jitter than rules with equal spread.
  • Quarterly accounting statistics will not be consistent over multiple years due to the yearly quarter containing the intercalary week having 14 weeks instead of the usual 13. This issue could arguably be minimised by placing the intercalary week at the end of the year.

References

  1. ^ "Leap Week Calendars". www.hermetic.ch. Retrieved 2023-05-17.

External links

This page was last edited on 2 August 2023, at 18:13
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