Persian calendar (strange calendar)

Compared with Coptic calendars, Persian calendars cannot be classified as "Lost calendars". The former originated from ancient times, but also from ancient Egyptian calendars; the Persian calendar is only pushed forward to the relatively closer 1079 AD, so this article is just another question. Currently, countries that pass through the Persian calendar include Iran and Afghanistan, and several other Central Asian countries.

Just like the current Gregorian calendar, Persian calendars are also pure solar calendars, and there are also the Jalali calendars originating in the Middle Ages and modern Persian calendars. The main difference is the stick rule.

The introduction of the Jalali calendar was introduced in March 15, 1079 by Omar Khayyam, an astronomy, mathematician and poet of the Royal Astronomical Observatory Isfahan. Previously, the solar calendar exists in the local region of Iran, but there is no concept of resettlement. Therefore, over time, it has brought great inconvenience to agricultural and tax affairs. Since then, the Jalali calendar has been in use for more than 800 years. It was not until March 31, 1925 that the Iranian Parliament decided to carry out the reform. In 1957, Afghanistan also adopted this calendar.

 

The year of the Persian calendar is also divided into 12 months, but different from the arrangement of the large and small calendar month, in the Persian calendar, the first six months of each year are large months, And the last six months are small months, the last month is the time of renewal, the 29 days of the year, and the 30 days of the year of the leap. The monthly names and corresponding days of the modern Persian calendar are as follows: Farvardin (frvrdyn, 31 days), ordibehesht (ardybhst, 31 days), Khordad (krdad, 31 days), and TIR (Tyr, 31 days), mordad (mrdad, 31 days), shahrivar (shryvr, 31 days), Mehr (MHR, 30 days), Aban (Aban, 30 days), Azar (AZR, 30 days), Dey (dy, 30 days), Bahman (bhmn, 30 days), esfand (asfnd, 29/30 days ). However, the names of Iran and today's Afghanistan before January 1, 1925 correspond to the Arabic names of the Zodiac constellation.

The first day of the year must be the time when the sun passes through the spring equinox. If it occurs before midday in Tehran time (specifically, when the east longitude reaches 52.5 degrees), the day is counted as the first day of the new year; otherwise, the next day is counted as the first day of the next year. The Persian New Year is called NOROUZ in Central Asia and is a very important holiday. The Persian calendar starts at the same time as the Islamic calendar. It is the year in which Muhammad took refuge from Mecca to Medina in 622 AD. The year suffix is AP, which is the abbreviation of Anno persico (or Anno persarum, that is, Persian calendar.

The monthly and monthly schedule is also unreasonable. As we all know, the Earth operates at uneven speeds in public transit orbit, and at a fast speed near the winter solstice point, and at a slow speed near the summer solstice. Therefore, it takes longer to run from the spring equinox to the summer solstice and from the summer solstice to the autumn equinox. The length of the first six months of the Persian calendar is longer than that of the last six months, at present, the first days of the three months of the last day are exactly the same as those of the summer solstice, the autumn equinox, and the winter solstice, facilitating the definition and differentiation of the season.

In fact, Persian calendars are more accurate than the Gregorian calendars. It is based entirely on the sun. As early as the era of Omar hyyam, the resettlement period has been determined to be 33 years and 8 years, so the average age is 365.2424 days, which is very close to the actual length of 365.2422 days in the year of return; in the modern Persian calendar, the rule of 683 decimal places was adopted. On average, the first four digits after the decimal point were the same, the accuracy has reached the level of 2 million years, which is only one day different from the actual sun operation.

It is difficult to calculate a leap year because the modern Persian calendar uses a large cycle and a small cycle. In 2820, there are 21 subcycles, each of which is in 128, and the last one is in 132. Each subcycle is divided into four small cycles: 29 years, 33 years, 33 years, and 33 years (for the last subcycle, It is 29, 33, 33, and 37 years ). In a small period of 29/33/37 years, a leap year is defined as long as the year is greater than 1 and is divisible by 4 and the remaining 1.

The modern Persian calendar is still relatively regular. For the calendar of the year before January 1925, omaer hyhamm only sets the principle of 8 hours for 33 years, it also brings a lot of trouble to the conversion. I made a lazy here, because of pure consideration of practical, unintentional investigation, to a link closed: http://www.payvand.com/calendar

In combination with accurate placement rules and reasonable monthly schedule, the short-term drift of the current Persian calendar season is very small, less than half a day, as shown in the following figure:

 

Image Source: answers.com

By the way, the week division in the Iran region starts from Monday or Sunday, but from Saturday, and from Friday to rest day. The day names are: shanbeh, yekshanbeh, doshanbeh, seshanbeh, chaharshanbeh, panjshanbeh, and jom'eh.

Conversion between Persian and Gregorian: http://www.netnative.com/calendar/

In addition to the Persian calendar, calendar-related articles are still to be written. As for the Islamic calendar that I am not very familiar with, there are other conversion software on hand, and it is not necessary to use Emacs for the time being, let's let it go first. Come back and have time to talk about it. It's so busy recently ......