Solar Hijri calendar

The Solar Hijri calendar (Persian: گاه‌شماری هجری خورشیدی‎, translit. gāh-shomāri-ye hejri-ye khorshidi; Pashto: لمريز لېږدیز کلیز‎), also called the Solar Hejri calendar^[1] or Shamsi Hijri calendar, and abbreviated as SH, is the official calendar of Iran and Afghanistan. It begins on the March equinox (Nowruz) as determined by astronomical calculation for the Iran Standard Time meridian (52.5°E or GMT+3.5h) and has years of 365 or 366 days.

Its determination of the start of each year is astronomically accurate year-to-year as opposed to the more fixed Gregorian calendar or "Common Era calendar", which averaged out, has the same year length, achieving the same accuracy (a more simply patterned calendar of 365 days for three consecutive years plus an extra day in the next year, save for exceptions to the latter in three out of every four centenaries). The start of the year and its number of days remain fixed to one of the two equinoxes, the astronomically important days which have the same duration of the sun. It results in less variability of all celestial bodies comparing a specific calendar date from one year to others.^[2]

Each of the twelve months corresponds with a zodiac sign. The first six months have 31 days, the next five have 30 days, and the last month has 29 days in usual years but 30 days in leap years. The New Year's Day always falls on the March equinox.

In Iran

A Persian contract published in Tehran on April 14, 1910 which used Lunar Hijri calendar.

On 21 February 1911, the second Iranian parliament adopted as the official calendar of Iran the Jalālī sidereal calendar with months bearing the names of the twelve constellations of the zodiac and the years named for the animals of the duodecennial cycle; it remained in use until 1925.^[1] The present Iranian calendar was legally adopted on 31 March 1925, under the early Pahlavi dynasty. The law said that the first day of the year should be the first day of spring in "the true solar year", "as it has been" ever so. It also fixed the number of days in each month, which previously varied by year with the sidereal zodiac. It revived the ancient Persian names, which are still used. It specified the origin of the calendar (Hegira of Muhammad from Mecca to Medina in 622 CE). It also deprecated the 12-year cycles of the Chinese-Uighur calendar which were not officially sanctioned but were commonly used.

The first six months (Farvardin–Shahrivar) have 31 days, the next five (Mehr–Bahman) have 30 days, and the last month (Esfand) has 29 days or 30 days in leap years. This is a simplification of the Jalali calendar, in which the commencement of the month is tied to the sun's passage from one zodiacal sign to the next. The sun is travelling fastest through the signs in early January (Dey) and slowest in early July (Tir). The current time between the vernal equinox and the autumnal equinox is about 186 days and 10 hours, the opposite duration about 178 days, 20 hours.

The Solar Hijri calendar produces a five-year leap year interval after about every seven four-year leap year intervals. It usually follows a 33-year subcycle with occasional interruptions by a single 29-year subcycle. The reason for this behaviour is (as explained above) that it tracks the observed vernal equinox. By contrast, some less accurate predictive algorithms are suggested based on confusion between the average tropical year (365.2422 days, approximated with 29 year, 33 year, and 37 year subcycles, 128-year and 132 year cycles, and 2820-year great cycles) and the mean interval between spring equinoxes (365.2424 days, approximated with a near 33-year cycle).

Earlier starting year (1976–1979)

In 1976, Shah Mohammad Reza Pahlavi changed the origin of the calendar to the beginning of Cyrus the Great's reign as the first year, rather than the Hejra of Muhammad. Overnight, the year changed from 1355 to 2535. The change lasted until the revolution in 1979, at which time the calendar reverted to Solar Hijri.^[3]

In Afghanistan

Afghanistan legally adopted the official Jalali calendar in 1922^[1] but with different month names. Afghanistan uses Arabic names of the zodiacal signs; for example the 1978 Saur Revolution took place in the second month of the Solar Hijri calendar (Persian Ordibehesht; Saur is named after Taurus). The Solar Hijri calendar is the official calendar of the government of Afghanistan, and all national holidays and administrative issues are fixed according to the Solar Hijri calendar.

Details of the modern calendar

The Solar Hijri calendar year begins at the start of spring in the Northern Hemisphere: on the midnight between the two consecutive solar noons, which include the instant of the March equinox, when the sun enters the Northern Hemisphere. Hence, the first noon is on the last day of one calendar year and the second noon is on the first day (Nowruz) of the next year.

Solar Hijri algorithmic calendar

The Solar Hijri (Persian) calendar is one of the oldest calendars in the world, as well as the most accurate solar calendar in use today. Since the calendar uses astronomical calculation for determining the vernal equinox, it has no intrinsic error, but this makes it an observation based calendar.^[6][7][8][9] Ahmad Birashk proposed an alternative means of determining leap years. His technique avoids the need to determine the moment of the astronomical equinox, replacing it with a very complex leap year structure. Years are grouped into cycles which begin with four normal years after which every fourth subsequent year in the cycle is a leap year. Cycles are grouped into grand cycles of either 128 years (composed of cycles of 29, 33, 33, and 33 years) or 132 years, containing cycles of 29, 33, 33, and 37 years. A great grand cycle is composed of 21 consecutive 128-year grand cycles and a final 132 grand cycle, for a total of 2820 years. The pattern of normal and leap years which began in 1925 will not repeat until the year 4745.

See also

• Iranian calendars
• Jalali calendar
• Iran Standard Time
• Royal stars
• Indian national calendar

References

Bibliography

• Panaino, Antonio (1990). "CALENDARS, i. Pre-Islamic calendars". Encyclopaedia Iranica. 4. ISBN 0-7100-9132-X.

External links

• How the leap years are calculated
• Meaning of the names of the months in the Persian Calendar
• Persian(shamsi)/Gregorian/Islamic(hijri) Windows Gadget – with persian occasions

Online calendars and converters

• An online Persian(shamsi)/Gregorian/Islamic(hijri) date converter on http://www.iranchamber.com
• Online Persian Calendar from aaahoo portal
• GFDL Afghan Calendar with Gregorian, Hejrah-e shamsi and Hejrah-e qamari dates

Programming

• GPL Iranian Calendar in JavaScript
• System.Globalization.PersianCalendar class documentation in MSDN Library (The implementation of Persian Calendar in Microsoft .NET Framework 2.0)
• Persian Zodiac a free, open source AIR application.