Hindu Calendar
Throughout most of history, most calendars were based on the moon and each waxing and waning of the moon would count as one month. One example of this is the Muslim Hijri calendar, which takes 12 lunar months. However, 12 lunar months are only 354 days, which is 11 days shorter than a solar year. This creates a problem because if people use a purely lunar calendar, the months in which spring, summer or winter occur will change from year to year (as the seasons depend on the earth’s movement around the sun). In fact, every few years, summer would occur in December!
The Hindu calendar is known as a lunisolar calendar. The 12 months move according to the moon and the year is 354 days long. However, every third year, 33 days (11 extra days * 3) are added by creating one extra lunar month of 29 days. The remaining four days are adjusted here and there.
The 12 Indian months are: Chaitra, Vaisakha, Jyeshtha, Ashadha, Shravana, Bhadra, Ashvin, Kartik, Agahana, Pausha, Magha, Phalguna. So every three years, one of these months occurs twice in the same year…it’s like having two Marches or two Julys in a year!
There are two main calendars in common use in India today, the Vikram Samvat with a zero point of 57 BC and the Shaka Samvat with a zero point of 78 AD. They are used for calculating the dates of all Hindu festivals like Diwali and Holi.
Hindu calendar, dating system used in India from about 1000 BCE and still used to establish dates of the Hindu religious year. It is based on a year of 12 lunar months; i.e., 12 full cycles of phases of the Moon. The discrepancy between the lunar year of about 354 days and the solar year of about 365 days is partially resolved by intercalation of an extra month every 30 months.
The Saka Calender is based on luni-solar reckoning of time. The calendar consists of 365 days and 12 months like the normal Gregorian calendar. Chaitra is the first month of the year beginning on March 22 which is the day after the Spring Equinox. During leap years, the starting day of Chaitra corresponds with March 21. To convert years in AD to Saka years, 78 must be subtracted for a date.
The names of the months in Saka Calendar are:
• Chhaitra (March 21 – April 20)
• Vaishakha (April 21-May 21)
• Jyeshtha (May 22-June 21)
• Ashadha (June 22- July 22)
• Shravana (July 23-August 22)
• Bhaadra (August 22-September 22)
• Ashwin (September 23-October 22)
• Kartika (October 23-November 21)
• Agrahayana (November 22-December 21)
• Pausha (December 22-January 20)
• Magha (January 21- February 19) and
• Phalguna (February 20-March 20/21)
The month of Chaitra has generally 30 days but there are 31 days during leap years. The months of Vaish?kha, Jy?shtha, ?sh?dha, Shr?vana, Bhaadra, have 31 days while the rest have 30 days. This is done by taking into account the ellipticity of earth’s orbit around the sun.
Computation and calculation of time was a hallmark of all ancient civilizations. Egyptian and Mesopotamian civilization had their abiding interest in chronology and astronomy. The oldest and the largest civilization, the Indus valley civilization, was by far the most advanced and sophisticated in terms of chronological and astronomical acumen. They even had professional astronomers, called ‘nakshatra darshaks’ or ‘star gazers’, who meticulously observed and recorded the phases of the moon in reference to fixed constellations of stars. This method of calculation and its precision, sharply distinguishes Indian astronomy from the astronomy of all other countries.
The Indian calendar is ingeniously based on both the sun as well as the moon. It uses a solar year, but divides it into 12 lunar months. A lunar month, is the time required for the moon to orbit once around the earth and pass through its complete cycle of phases. Furthermore, these months are formulated in accordance with the successive entrances of the sun into the 12 rashis or the signs of the zodiac derived from the 12 constellations marking the path of the sun.
Vedic literature show that the knowledge of chronology (science of Time) and chronometry (scientific measurement of Time) existed even during Vedic times, thousands of years before the Christian era. Knowledge of planetary motions, constellations, eclipses, solstices, seasons, etc. has existed since the beginning of the Vedic age. A method of distributing time into various periods such as days, fortnights, months and years was adopted for the purposes of civic life, these divisions being intimately connected with the affairs of the people. And because of the very fact that the Indian calendar was devised to serve the affairs of day-to-day living, it was allowed the freedom of being both lunar and solar. The Rig Veda, cites months being lunar, but years luni-solar.
This means that there was a constant correlation between the solar year and its monthly lunar divisions. A lunar month is precisely 29 days 12 hours 44 minutes and 3 seconds long. Twelve such months constitute a lunar year of 354 days 8 hours 48 minutes and 36 seconds. To help the lunar months coincide with the solar year, the practice arose of inserting intercalary (extra) months. In general, 60 solar months = 62 lunar months. And so an extra month, called the Adhik Maas (extra month), is inserted every 30 months, approximately every 2½ years. Such a practice was prevalent even in Vedic times. An intercalary month mentioned in the Rig Veda {Vedamãso dhrutavrato dvãdasha prajãvatah; vedã ya upajãyate. (I/25:8)} proves that the month was added to preserve the correspondence between a whole solar year and the 12 lunations.
Seasons within the Hindu calendar
It is even more interesting, how the solar year was classified on the basis of seasons. The 12 lunar months of a solar year are divided into six ritus (seasons), each comprising of approximately two months. Since the seasons are solar based, each of the six seasons — Sharad (late monsoon), Hemant (early winter), Shishir (winter), Vasant (spring), Grishma (summer) and Varsha (monsoon)- commence around the 21st date (±2) of each even month of the Western calendar.
The Hindu calendar recognizes the importance of the summer solstice and winter solstice in a solar year, determining the six seasons. The Dakshinayana or the sun’s southern course starts from June 21 till December 21, during which the day-length is successively getting shorter until it is the shortest in december. The Uttarayana or the sun’s northern course progresses from December 21 until June 21, during which the day-length gets successively longer until it is the longest in June. Sun reaches the equinox twice in a year, during which the length of day and night are equal. The first point is Vernal Equinox in March 20(Vasant Sampaat). The other point is called Autumnal Equinox in September 22(Sharad Sampaat).