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+# A Calendar for Time to Come
+
+A perennial solar calendar based on astronomical observations.
+
+The calendar year consists of 360 calendar days + 5 intercalary days (6 in leap years), divided into 4 equal quarters of 1 intercalary day + 90 calendar days. The remaining 1 or 2 days of the year are intercalary transition days between years.
+
+The 360 calendar days may be divided into eight 45-day months, as well as 40 x 9-day weeks (3 x 3 days). Alternatively, one can use the more traditional twelve 30-day months.
+
+The calendar year begins at the midnight closest to the instant of the northward equinox as measured from the prime meridian. Consequently, if the northward equinox falls before solar noon on a particular day, then that day is the first day of the year. If the northward equinox occurs after solar noon, the following day begins the calendar year.
+
+The calendar's proposed epoch is the beginning of the human era (10001 BC).
+
+Essentially, it's the Persian calendar with a different division of the year, a different meridian and a different epoch. The calendar and its astronomical basis is deeply indebted to Persian astronomer Omar Khayyam's 11th century reform of the Jalali calendar.
+
+### Advantages
+
+- **[Accurate](#accuracy)** — follows the true solar year and its seasons
+- **Balanced** – division of the year into equal parts
+- **Dynamic** — grouping of days into 3 × 3 is a [powerful concept](https://www.hermetic.ch/cal_stud/ltc/ltc.htm#advantages)
+- **Predictable** — has a consistent, perennial structure
+- **Simple** — easy to learn and uncomplicated to use
+
+It is structured, yet flexible enough to adapt to different uses and cultures:
+  - **Agriculture** — follows natural cycles
+  - **Business** — divided into equal parts, allows for flexible schedules
+  - **Civil** — simple and predictable
+
+The calendar is not tied to any culture/religion, except inevitably to that of the current scientific paradigm. While it is scientifically grounded, it does not oppose combination with cultural or religious concepts.
+
+### Disadvantages
+
+- **No simple leap year rule** — a tradeoff for astronomical accuracy
+- **Unfamiliarity** — new divisions, units and beginning of year
+- **Yet another calendar** — made by some commoner named Joakim (who is not the pope)
+
+### Accuracy
+
+Observation-based calendars embrace the non-uniform motion of the Earth around the Sun, as well as the short-term perturbations. The future can never be predicted with absolute certainty, due to the dynamic nature of the universe. The only way to know with absolute certainty the length of the year is through observation.
+
+Calendars based on the Jalali calendar are the most accurate in relation to the true solar year. Today's astronomical knowledge and computing power enable us to predict with very high precision the instant of the northward equinox. The exact instant can now be measured to an accuracy of better than 1 millisecond ([Heydari-Malayeri, 2004](http://aramis.obspm.fr/~heydari/divers/ir-cal-eng.html)).
+
+### Summary
+
+- A [perennial](https://en.wikipedia.org/wiki/Perennial_calendar) [solar calendar](https://en.wikipedia.org/wiki/Solar_calendar) for Earth based on astronomical observations
+  - Standing on the shoulders of the Persian [Solar Hijri](https://en.wikipedia.org/wiki/Solar_Hijri_calendar) and [Jalali](https://en.wikipedia.org/wiki/Jalali_calendar) calendars
+  - With roots in the [Zoroastrian calendar](https://en.wikipedia.org/wiki/Zoroastrian_calendar) and possibly the [Egyptian calendar](https://en.wikipedia.org/wiki/Egyptian_calendar)
+- The [calendar year](https://en.wikipedia.org/wiki/Calendar_year) begins at the [northward equinox](https://en.wikipedia.org/wiki/March_equinox) measured from the [prime meridian](https://en.wikipedia.org/wiki/Prime_meridian)
+- 360 calendar days + 5 or 6 [intercalary](https://en.wikipedia.org/wiki/Intercalation_(timekeeping)#Solar_calendars) days
+  - 4 quarters of 90 calendar days + 1 intercalary day
+  - 8 "months" of 45 calendar days
+  - 40 "weeks" of 9 calendar days
+    - 3 × 3 days (based on the tridays of the [Liberalia Triday Calendar](https://www.hermetic.ch/cal_stud/ltc/ltc.htm))
+  - 1 or 2 intercalary transition days at the end of the year
+- Proposed [epoch](https://en.wikipedia.org/wiki/Epoch) is the beginning of the human era (10001 BC)
+
+For more details, see the [definition](definition.md) or the [FAQ](faq.md).
+
+## What it is not
+
+#### This calendar does not attempt to:
+
+- Reform an existing calendar
+- Incorporate the traditional 7-day week in its structure
+- Incorporate the [lunar phases](https://en.wikipedia.org/wiki/Lunar_phase), as [lunisolar calendars](https://en.wikipedia.org/wiki/Lunisolar_calendar) are inherently complex and irregular
+- Accurately follow the [astronomical seasons](https://en.wikipedia.org/wiki/Season#Astronomical), as their lengths change over time
+- Align with the [zodiac](https://en.wikipedia.org/wiki/Zodiac), due to the (lunisolar) [precession of the ecliptic](https://en.wikipedia.org/wiki/Axial_precession)
+- Introduce time scales or prescribe holidays — it's just a calendar
+
+However, features like these may be applied, just as they are applied to existing calendars. For example, the unbroken chain of 7-day weeks may be used just like in the Gregorian calendar, with weekdays retaining their traditional names and cultural/religious significance, if so is desired. As long as the calendar's underlying structure remains the same.
+
+#### Related proposed calendars:
+
+- Isaac Asimov's [World Season Calendar](https://calendars.wikia.org/wiki/World_Season_Calendar)
+- Peter Meyer's [Liberalia Triday Calendar](https://www.hermetic.ch/cal_stud/ltc/ltc.htm)
+- Alexander Laik's [Calendar of the Rainbow](https://calendars.wikia.org/wiki/Calendar_of_the_Rainbow)
+- [The Dee-Cecil Calendar](https://www.hermetic.ch/cal_stud/gods_longitude.htm)
+- [The World Calendar](http://myweb.ecu.edu/mccartyr/world-calendar.html)
+- [The Primavera Calendar](http://bosonline.com/primavera/)
+- [Universal Celestial Calendar](https://www.universalcelestialcalendar.com/)
+- [The Earth Epic Calendar](https://earthepiccalendar.com/current-calendar/)
+- [Albertan Calendar](https://calendars.wikia.org/wiki/Albertan_calendar)
+
+---
+
+#### References:
+
+- [A concise review of the Iranian calendar](http://aramis.obspm.fr/~heydari/divers/ir-cal-eng.html) (Heydari-Malayeri, 2004)
+- [More Mathematical Astronomy Morsels](https://www.willbell.com/math/moremorsels.HTM) (Meeus, 2002)
+- [The Liberalia Triday Calendar](https://www.hermetic.ch/cal_stud/ltc/ltc.htm) (Meyer, 1999)
+
+#### Recommended links:
+
+- [Calendar Reform](http://myweb.ecu.edu/mccartyr/calendar-reform.html) (McCarty)
+- [Calendars New and Old](https://www.hermetic.ch/cal_stud.htm) (Meyer)
+  - [The Non-implemented 33-Year English Protestant Calendar](https://www.hermetic.ch/cal_stud/dst01.htm) (Steel, 1999)
+  - [How Britain got the Calendar Wrong](https://www.hermetic.ch/cal_stud/dst02.htm) (Steel, 1999)
+- [One Day Too Many](http://www.schlag.name/calendarreform00.htm) (Schlag)  
+  <small><em>Doesn't mention the Persian calendar. This calendar would also solve all the [faults](http://www.schlag.name/calendarreform11.html) of the Gregorian calendar.</em></small>
+- [The Persian calendar for 3000 years](http://www.astro.uni.torun.pl/~kb/Papers/EMP/PersianC-EMP.htm) (Borkowski, 1996)