The Gregorian calendar is the calendar used in most of the world. It is named after Pope Gregory XIII, who introduced it in October 1582.
While the calendar is renowned for its accuracy, there are some issues in the organization of the calendar:
Thirty days hath September,Doomsday Rule
April, June, and November,
All the rest have thirty-one,
But February's twenty-eight,
The LEAP YEAR, which comes once in four,
Gives February one day more.
There are several proposed calendar reforms. I have programmed six calendar converters, which can be found by clicking on their respective hyperlinks below.
These calendar programs are programmed in Javascript and organized in an interactive HTML page. They are all spawned from the International Fixed Calendar (IFC) program. Initially developed in CodeHS on a CodeHS canvas, the IFC program was modified to operate on an HTML webpage for easier use and programability. The other calendars are spawned from this code, with modifications to the year start, and/or month length and number of months.
An issue previousl present in these programs was the conversion system, stemmed from dividing the number of days from the year start. On desktop, the user's date was limited to between January 1 and December 1 of a common year. However, a person on a mobile device can circumvent this limit, rendering undersirable output, as at the time, there was no failsafe to this issue. On October 23, 2020, all calendar programs recieved a modification which enabled the calendar program to operate properly for all dates and years.
diffDays -= Math.floor(365.2425*(Math.floor(Days/365.2425)))
If the day goes over the number of days in that year, the exceeding number of days are removed. 365.2425 is the number of days in the Gregorian calendar, the calendar currently in use (as of October 23, 2020), which is used to calculate the dates to and from the respective calendar reforms.
| Calendar | Key Dates |
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| International Fixed Calendar |
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| French Republican Calendar |
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| 13 Moon Calendar |
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| The New Calendar |
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| Solstice Calendar |
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| Reddit 8 Day Week Calendar |
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These calendars are also programmed in Javascript and organized in an interactive HTML page. Users input information to output custom calendars.
| Calendar | Key Dates |
|---|---|
| School Calendar Generator |
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| Make Your Own Calendar |
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There have been several proposals for a 13-month calendar. Each month has 28 days, with one day left over in a common year (Year Day) and another day left over in a Leap Year (Leap Day). The left subcolumn of each column lists the month names, while the right subcolumn lists the Gregorian dates the months encompass.
| International Fixed Calendar | Solstice Calendar | 13 Moon Calendar | |||
|---|---|---|---|---|---|
| Year begins January 1 | Year begins on the Norther Winter Solstice | Year begins on some other date | |||
| International Fixed Calendar
Twelve months are named and ordered the same as those of the Gregorian calendar, except for the extra month inserted between June and July, and called Sol. Situated in mid-summer (from the point of view of its Northern Hemisphere authors) and including the mid-year solstice, the name of the new month was chosen in homage to the sun. |
Solstice Calendar (Ends the year on the Winter Solstice, Starts year December 22) Year starts December 22, Gregorian, (marked as Solstice 1) the day after the Solstice (Winter in the Northern Hemisphere, Summer in the Southern Hemisphere) This is 10 days before the tradtional start of the Gregorian Year, January 1CAL13 FIXED CALENDAR The calendar has 13 months of 28 days. It has two varieties: Starts the year on the Winter Solstice, December 21: Common Years, Leap Years Start the year on January 1: Common Years, Leap Years |
13 Moon calendar
13 Moon Calendar Matching Dates on Gregorian Year starts on July 26 Gregorian. Year day is July 25 Gregorian |
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| January | January 1 - January 28 | Solstice | December 22 - January 18 | Magnetic Moon | July 26 - August 22 |
| Februrary | January 29 - Februrary 25 | Mercury | January 19 - Februrary 15 | Lunar Moon | August 23 - September 19 |
| March | Februrary 26 - March 25* | Venus | Februrary 16 - March 15* | Electric Moon | September 20 - October 17 |
| April | March 26* - April 22* | Gaia | March 16* - April 12* | Self-Existing Moon | October 18 - November 14 |
| May | April 23* - May 20* | Luna | April 13* - May 10* | Overtone Moon | November 15 - December 12 |
| June |
May 21* - June 17*
June 17 = Leap Day |
Martian | May 11* - June 7* | Rhythmic Moon | December 13 - January 9 |
| Sol | June 18 - July 15 | Asteroid | June 8* - July 5* | Resonant Moon | January 10 - Februrary 6 |
| July | July 16 - August 12 | Jupiter | July 6* - August 2* | Galactic Moon | Februrary 7 - March 6* |
| August | August 13 - September 9 | Saturn | August 3* - August 30* | Solar Moon | March 7* - April 3* |
| September | September 10 - October 7 | Uranus | August 31* - September 27* | Planetary Moon | April 4* - May 1* |
| October | October 8 - November 4 | Neptune | September 28* - October 25* | Spectral Moon | May 2* - May 29* |
| November | November 5 - December 2 | Pluto | October 26* - November 22* | Crystal Moon | May 30* - June 26* |
| December |
December 3 - December 30 December 31 = Year Day |
Comet |
November 22* - December 21* On Common Years: December 21 = Year Day (December 29 on Solstice Calendar)On Leap Years: December 20 = Year Day (December 29 on Solstice Calendar) December 21 = Leap Day (December 30 on Solstice calendar) |
Cosmic Moon |
June 26* - July 24* On Common Years: July 25 = "Day Without Time" (Year Day) On Leap Years: July 24 = "Day Without Time" (Year Day) July 25 = Leap Day |
*IFC: These Gregorian dates between March and June are a day earlier in a Gregorian leap year. March in the Fixed Calendar always has a fixed number of days (28), and includes the Gregorian February 29 (on Gregorian leap years).
*Solstice Calendar: These dates after after March are a day earlier in a Gregorian leap year. March in this calendar always has a fixed number of days (28), and includes the Gregorian Februrary 29 (on Greogrian leap years)
*13 Moon Calendar:These dates after after Gregorian March are a day earlier in a Gregorian leap year. Galactic Moon in this calendar always has a fixed number of days (28), and includes the Gregorian Februrary 29 (on Greogrian leap years)
Solstice Calendar
: A calendar that starts the year on the Winter Solstice.
Also converts the date.
The Solstice Calendar names the first month Solstice after the Solstice which marks the end of the year. Then the other 12 months are named after the cellestial bodies of the Solar System: Mercury, Venus, Earth, The Moon, Mars, The Asteroid Belt, Jupiter, Satrn, Uranus, Neptune, Pluto and Comet (Oort Cloud bodies, like Halley's Comet) uses the modern names for the planets.
Roman and Greek god names
https://coolcosmos.ipac.caltech.edu/ask/196-How-did-the-planets-get-their-names-
http://www.solsticecalendar.com/tag/13-month-calendar-system/
4th month named after Earth
Other calendar reforms seek to maintain a year with 12 months. 12 is divisible by 2 (halves), 3 (thirds), 4 (quarters) and 6 (sixths)
| Reddit 8 Day Week Calendar | French Republican Calendar |
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Sansculottides (Complmentary Days)Five extra days – six in leap years – were national holidays at the end of every year. These were originally known as les sans-culottides (after sans-culottes), but after year III (1795) as les jours complémentaires:
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The New Calendar divides the year into 5 seasons. Each week is 9 days long and each seasons consists of 8 of them, with an extra day in the middle, making each season 73 days.