Hindu Calendar-2

 Measurement of time 

One of the most striking features of the Hindu calendar system is its intricacy. It offers a multidimensional method of structuring time, combining information about lunar days, solar days, lunar months, solar months, the Sun's and the Moon's movements in relation to stellar constellations, and other astronomically defined time spans. This makes the Hindu calendar vastly more complex than the Western calendar, which is built around only two basic units of time: solar days and solar years.

The Flux of Time is apparently, without a beginning or end, but it is cut up periodically by several natural phenomena,

• The ever-recurring alternation of daylight and night defined a day
• The recurrence of the moon's phases, defined as a month
• The recurrence of seasons, defined as a year

It is this recurring phenomenon which is used to make a calendar.

In the Vedic period, they observed and used these very natural phenomena to record the passage of time.  My blog Vedic Period 2  explains

Day

The time from sunrise to sunrise gives us a natural solar day or a Savana day. The Jews Babylonians and Muslims/ Hijri calendars calculate from sunset to sunset. Gregorian calendars calculate from midnight to midnight.

The mean solar day is used for calendar purposes, as the length of a solar day is variable.

A sidereal day is a period between two successive transits of a fixed star, and by the astronomical definition, it is the transits of the first point of Aries.(The First Point of Aries is a fiducial Point)

A solar day is longer than a sidereal day.

Indian calendars use ‘तिथि’ to denote a lunar day. This is specific to the Indian calendar/Panchang and is nowhere seen in other calendars. तिथि will be explained in detail later.

Month

A month, known as Chandra mana or masa, is primarily a lunar phenomenon. Its duration is defined as the time elapsed between two lunations, which can be from the new moon to the new moon or from the full moon to the full moon. The average length of a mean synodic period is taken to be approximately 29.5 days. This month is further divided into two halves, referred to, as paksha, and into 30 segments known as Tithis.

Year

There are three types of years

Solar/Tropical Year –It is, the time taken by the Earth to move from equinox to equinox or tropics or season to season. Indian calendars call it ‘Varsha’ which also denotes the rainy season.

Sidereal Year- It is, the time taken by the Earth to make one revolution around the Sun with respect to a fixed star.

Anomalistic Year- It is, the time taken by the Earth to make one revolution from Aphelion to Aphelion (Aphelion-furthermost point from the Sun) or Perihelion to Perihelion. (Perihelion -the nearest  point from the Sun)

The sidereal year is greater than Solar/Tropical Year. These years are considered for calendar purposes.

For divisions of day month and year during the Vedic period see the blog Vedic Period 2

The primary aspect of any calendar is to measure the correct duration of a year. Once the duration is ascertained, the other time units are calculated accordingly.

The length of the year, as counted in Vedic and later in the Vedang period was 360 and 366 days. It was later corrected during Arya Sidhant period to 365d 6h 12m and then later adjusted to the modern value of 365d 5h 48 m. The sole aim of correction is to keep the calendars in sync with the actual positions on the ecliptic and the seasons. 

Elements and Definitions

पंचांग

This calendar is highly comprehensive, integrating various elements such as ephemeris data, rituals, and both astronomical and astrological information. It has developed over time to adapt to evolving needs and may exhibit slight variations depending on the region.

 As the name suggests it is composed of 5 elements पंच अंग = पंचांग. These elements are

•  वार् 
• तिथि 
• नक्षत्र
• योग
• करण 

The earliest calendar mentioned only तिथि and नक्षत्र. Other elements were added later on. 

वार्

A natural solar day called ‘Savan divas’ सवन दिवस'

The nakshatra names were used to name the 'days' during the Vedic period. Thus when the moon is expected to be found in the मघा नक्षत्र(Alpha Leonis). The day would be called the मघा day. However, this system was discontinued later.

The present name and order of the days were borrowed from the Chaldeans and introduced in Hindu astronomy around 500 BCE. A वार् begins at sunrise, and seven वार् compose a week.

Some common names of these days are

• Sunday- आदि,आदित्य,रवि,अहस्कर,अर्क,अरुणा,भट्टारक,अहरपति,भास्करः,ब्रध्णः,भानु
• Monday. सोम , अबज, चन्द्र, चन्द्र, इन्दु, निष्पति, क्षापकर,
• Tuesday.  मंगल, अंगारक, भौम, महिसुता ,रोहितांग.
• Wednesday.बुध ,बौध, रौहिनेय, सौम्या
• Thursday. गुरु, अंगिरस, बृहस्पति, धीषण, सुरचार्य, वाचस्पति.
• Friday.. शुक्र ,भार्गवं, भृगुं ,दैत्यगुरुं, काव्यं ,उसनानि, कवि
• Saturday. शनि, सौरी, मंद

The solar day (savan divas) is further divided as,

• 60 Ghatikas = 1divas /1 solar day.
• 1 Ghatika =60 Pal=24 Minutes
• 1 Pal=60 Vipal=24 Seconds
• 1 Vipal=60 Prativipal=0.4 Second        

 For more on day division see Vedic Period 2

तिथि

To put it in simple words, a तिथि is a lunar day, and it relates to the Hindu lunar calendar. It is the exact point of time when the moon, moving eastwards from the sun after the अमावस्या, leaves the sun behind by 12 degrees, is the first तिथि, called  प्रथमा or प्रतिपदा and so on till the complete synodic revolution of the moon or one lunation occupying 30 तिथि for the 360 degrees to denote 1 lunar month. Since, however, the motions of the sun, earth and the moon are always varying in speed the length of a तिथि constantly alters.

• The greatest length is 26 h 6m 24s
• The least length is 21 h 34m 24s. 
• An average or mean length of 23h 37m 28.09s is considered for calendric purposes.

The तिथि1 to 15 are named Pratipada, Dwitiya,Tritiya ….Poornima / Amavasya (Full or New Moon)

 नक्षत्र 

This is specific to the Hindu calendar, like Tithi. There are 27 Nakshatra along the ecliptic. Each nakshatra occupies 360/27= 13 deg 20 min of space along the ecliptic. The equal division is for ease of calculation. In actuality,  नक्षत्र  occupies a varying space ranging from 12 to 18 degrees, approximately. Because of the variable motions of the Moon, the Sun and Earth, the time the Moon takes to traverse one nakshatra ranges from 

• A maximum length of  26h 32m 24s. 
• A minimum length of 22h 22m 24s 
• The mean length of Moon nakshatra is taken as 24h 17m 9.3s

The system of starting the list of nakshatra from Ashwini came into vogue around the seventh century BCE. For details on नक्षत्र  see blog Vedic Pd 4

योग

Astronomically, a योग corresponds to 13 degrees and 20 minutes—being the sum of the Longitudes of the Sun and the Moon. That is, it is the time during which the Sun and the Moon together cover 13 degrees and 20 minutes of space. But there is no direct astronomical phenomena corresponding to it. There are 27 योग in number. The concept of योग arose sometime around 700 CE and became an integral part of  पंचांग only after around 700 CE.

करण

A करण being half a tithi, or the time during which the difference of longitudes of the Sun and Moon are increased by 6 degrees. There are 60 करण in a lunar month. There are seven करण in a series of eight cycles—a total of 56—every month, from the second half of शुक्ल प्रतिपदा(1st) to the end of the first half of कृष्ण पक्ष चतुर्दशी (14th). The other four करण are respectively from the second half ofकृष्ण पक्ष चतुर्दशी(14th) to the end of the first half of शुक्ल प्रतिपदा.

योग and करण are NOT used for calendric purposes but only for Astrological purposes.

 

 ..................to be continued with the construction of calendars, dating and Era's

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References:-

1.  Bhartiya Jyotish Shastra-SB Dixit
2. The Indian Calendar-Robert Sewell and SB Dixit
3. Cowasjee Patells Chronology
4. The book of Eras- Gen A Cunningham
5. Calendar Reforms Committee Report 
6. Ancient Indian Astronomy -RN Iyengar
7. The Calendars of India- VK Mishra