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# चान्द्रम् ॥ Of Chandra
# चान्द्रम् ॥ Of Chandra
# आर्क्षम् (नाक्षत्रम्) ॥ Aarksham (Of Nakshatra)
# आर्क्षम् (नाक्षत्रम्) ॥ Aarksham (Of Nakshatra)
The Manas which are used in daily activities are four in number - सौरचान्द्रार्क्षसावनैः । Solar, Lunar, Sidereal, and the Savana (Civil). The Mana of Jupiter (Barhaspatya) is used for determining the Shasthtyabda (60 Samvatsaras) celebration while the remaining four are not used on a daily basis.<ref name=":1">Pt Mahavir Prasad Srivastav (1940 First Edition) ''Surya Siddhanta with Vijnana Bhashya, Parts 1 and 2.'' Allahabad: Dr. Ratnakumari Svadhyaya Sansthan. (Page 794 -)</ref>
The Manas which are used in daily activities are four in number - सौरचान्द्रार्क्षसावनैः । Solar, Lunar, Sidereal, and the Savana (Civil). The Mana of Jupiter (Barhaspatya) is used for determining the Shasthtyabda (60 Samvatsaras) or attaining 60 years of age while the remaining four are not used on a daily basis.<ref name=":1">Pt Mahavir Prasad Srivastav (1940 First Edition) ''Surya Siddhanta with Vijnana Bhashya, Parts 1 and 2.'' Allahabad: Dr. Ratnakumari Svadhyaya Sansthan. (Page 794 -)</ref>
== दिननिर्नयम् ॥ Dina Nirnaya ==
== दिननिर्नयम् ॥ Dina Nirnaya ==
We see in the sky that due to diurnal motion, the Sun rises in the eastern horizon, moves up in the sky westward and sets in the western horizon. From the sunset to the next sunrise, it will be below the horizon during the night. It is common knowledge all over the world that this period of time between the sunrise and sunset is called a Day. However, our seers have calculated and defined a Day, not just with respect to the Sun but also with other cosmic references and specified where such a measure of time is to be used.
It is long known to our ancient seers that it is the earth that revolves around the sun in an ecliptic path. However, the time is calculated based on using the earth as a reference, and thus we say sun is revolving around the earth. We see in the sky that due to diurnal motion, the Sun rises in the eastern horizon, moves up in the sky westward and sets in the western horizon. From the sunset to the next sunrise, it will be below the horizon during the night. It is common knowledge all over the world that this period of time between the sunrise and sunset is called a Day. However, our seers have calculated and defined a Day, not just with respect to the Earth but also with other cosmic references and specified where such a measure of time is to be used.
=== सौरदिनम् ॥ Saura Dina (Solar Day) ===
<blockquote>सौरेण द्युनिशोर्मानं षडशीतिमुखानि च। अयनं विषुवच्चैव सम्क्रान्तेः पुण्यकालता॥ (Sury. Siddh. 14.3)<ref name=":0" /></blockquote>With reference to Earth the Sun's motion along the ecliptic path, in the rashi, is about 1° per day. This is called a Solar Day.
==== षडशीतिमुखानि ॥ Shadasheeti Mukhas ====
तुलादि षडशीत्यह्नाम् षडशीतिमुखम् क्रमात् । तच्चतुष्टयम् एव स्याद् द्विस्वभावेषु राशिषु ॥
षड्विम्शे धनुषो भागे द्वाविम्शे निमिषस्य च । मिथुनाष्टादशे भागे कन्यायास् तु चतुर्दश॥
==== Vishuvats ====
ततः शेषाणि कन्याया यान्य् अहानि तु षोडश । क्रतुभिस् तानि तुल्यानि पितृऋणाम् दत्तम् अक्षयम् ॥
'''1 Saura Dina (Solar Day) = Movement of Sun in a Rashi by 1 degree in ecliptic path'''
==== Purpose of Saura Dina ====
# Determining the length of the day and night
# Shadashiiti Mukhas
# Determine Uttarayana and Dakshinayana (the northern and southern paths of the Sun)
# Equinoxes and Vishuvats
# Sankrantis (the time of entry of Sun into a new rashi)
=== सावनदिनम्॥ Savana Dina (Civil Day) ===
=== सावनदिनम्॥ Savana Dina (Civil Day) ===
<blockquote>उदयाद् उदयम् भानोः सावनम् तत् प्रकीर्त्यते । सावनानि स्युरेतानि यज्ञकालविधिस्तु तैः ॥ </blockquote><blockquote>सूतकादिपरिच्छेदो दिनमासाब्दपास्तथा । मध्यमा ग्रहभुक्तिस्च सावनेन प्रकीर्त्यते ॥ (Sury. Siddh. 14.18)<ref name=":0" /></blockquote>The duration between two successive risings of the Sun is called a Savana Dina or Civil Day, a Solar Day.<ref name=":1" />
<blockquote>उदयाद् उदयम् भानोः सावनम् तत् प्रकीर्त्यते । सावनानि स्युरेतानि यज्ञकालविधिस्तु तैः ॥ </blockquote><blockquote>सूतकादिपरिच्छेदो दिनमासाब्दपास्तथा । मध्यमा ग्रहभुक्तिस्च सावनेन प्रकीर्त्यते ॥ (Sury. Siddh. 14.18)<ref name=":0" /></blockquote>The duration between two successive risings of the Sun is called a Savana Dina or Civil Day.<ref name=":1" />
Observations of sunrise over a very long time has revealed that the duration of a day is not constant but varies from day to day although very slightly. An average calculated based on the observations is referred to as the Mean Solar Day or Mean Civil day. Savana Dina is divided into 60 equal parts called Ghatikas or 24 equal parts called Hora (hours). Thus the 24 hour day that is used for our regular daily activities is the Savana Dina.<ref name=":0" />
Observations of sunrise over a very long time has revealed that the duration of a day is not constant but varies from day to day although very slightly. An average calculated based on the observations is referred to as the Mean Solar Day or Mean Civil day. Savana Dina is divided into 60 equal parts called Ghatikas or 24 equal parts called Hora (hours). Thus the 24 hour day that is used for our regular daily activities is the Savana Dina.<ref name=":2">Rao, S. Balachandra. (2000) ''Indian Astronomy, An Introduction.'' Hyderabad: Universities Press (India) Limited. (Page 39-50)</ref>
'''1 Savana Day (Civil Day) = 24 Hours'''
==== Purpose of Savana Dina ====
==== Purpose of Savana Dina ====
# Determine the rulers of the day, month and year
# Determine the rulers of the day, month and year
# To calculate the mean motion of planets.
# To calculate the mean motion of planets.
=== तिथिः ॥ Tithi (Lunar Day) ===
<blockquote>अर्काद्विनिस्सृतः प्राचीं यद्यात्यहरहश्शशी। तच्चान्द्रमानम् अम्शैस्तु ज्ञेया द्वादशभिस्तिथिः॥ </blockquote><blockquote>तिथिः करणम् उद्वाहः क्षौरम् सर्वक्रियास् तथा। व्रतोपवासयात्राणाम् क्रिया चान्द्रेण गृह्यते॥ (Sury. Siddh. 14.12-13)<ref name=":0" /></blockquote>The time in which the Moon being separate from the Sun (after a conjunction) moves daily to the east is the measurement for the moon (चान्द्रमानम्) Chandra Mana. The time taken by the Moon to cover exactly an amount of 12° relative to the Sun, is defined as Tithi or Lunar Day.<ref name=":1" />
Since the moon moves faster than the sun, starting from a new moon, the moon gains about 12° per day over the Sun, i.e., one Tithi per day, thus the chandra masa has 30 tithis. The half-lunar month from a new moon to the succeeding full moon is called Shukla Paksha (the bright fortnight) and the other half-lunar month from the full moon to next new moon is called Krshna Paksha (dark fortnight). The lunar month is a natural unit for a month. It is important to note that the beginning and end of a lunar month are naturally marked by two successive new moons.<ref name=":2" />
==== Purpose of Chandra Mana ====
# Determination of Tithi, Karana (half of Tithi)
# Determine the time for samskaras like marriage
# Determine the appropriate time for activities such as shaving, tonsure
# To determine the time for Vratas, Upavasas, Yatras
=== नाक्षत्रदिनम् ॥ Nakshatra Dina (Sidereal Day) ===
=== नाक्षत्रदिनम् ॥ Nakshatra Dina (Sidereal Day) ===
भचक्रभ्रमणम् नित्यम् नाक्षत्रम् दिनम् उच्यते। नक्षत्रनाम्ना मासास् तु ज्ञेयाः पर्वान्तयोगतः ॥(Sury. Siddh. 14.15)<ref name=":0" />
<blockquote>भचक्रभ्रमणम् नित्यम् नाक्षत्रम् दिनम् उच्यते। नक्षत्रनाम्ना मासास् तु ज्ञेयाः पर्वान्तयोगतः ॥ (Sury. Siddh. 14.15)<ref name=":0" /></blockquote>The time taken for one revolution of the sphere of stars is called a sidereal day.
The time taken by the fixed stars to go around the earth is called a Nakshatra Dina or Sidereal Day; and this time is equal to the period of the rotation of the Earth. Sidereal is a term used to refer to stars. It is important to note that the time taken by the fixed stars to go round the Earth once is not the same as that taken by the Sun. While all the celestial bodies appear to move from the east to west due to the diurnal motion, the Sun would have moved from west to east along the ecliptic by about 1°, relative to the stars. Therefore, the fixed stars take a little less than 24 hours (mean civil day) to complete a rotation around the Earth. As a natural consequence if a particular star rises in the eastern horizon at a particular time today, it will rise about two hours earlier after 30 days, 4 hours earlier after 60 days, and so on.
The time taken by the fixed stars to go around the earth is called a Nakshatra Dina or Sidereal Day; and this time is equal to the period of the rotation of the Earth. Sidereal is a term used to refer to stars. It is important to note that the time taken by the fixed stars to go round the Earth once is not the same as that taken by the Sun. While all the celestial bodies appear to move from the east to west due to the diurnal motion, the Sun would have moved from west to east along the ecliptic by about 1°, relative to the stars. Therefore, the fixed stars take a little less than 24 hours (mean civil day) to complete a rotation around the Earth. As a natural consequence if a particular star rises in the eastern horizon at a particular time today, it will rise about two hours earlier after 30 days, 4 hours earlier after 60 days, and so on.
It is found that the fixed stars take about 3 minutes 56 seconds less than the Sun to go round the Earth once.
It is found that the fixed stars take about 3 minutes 56 seconds less than the Sun to go round the Earth once.
'''1 Nakshatra Dina = 1 Savana Dina - 3 mins 56 secs = 23 Hrs 56 Mins 4 Secs'''
==== Purpose of Nakshatra Dina ====
# Naming of lunar months is from the Nakshatras; the name of a lunar month is determined from the nakshatra in which moon is present at the time of Purnima (15th day of full moon) tithi (with a few exceptions).
=== Summary ===
1 Saura Dina (Solar Day) = Movement of Sun in the Rashi by 1 degree
1 Tithi (Lunar Day) =
1 Savana Dina (Civil Day) = 24 hours
1 Nakshatra Dina (Sidereal Day) = 23 Hrs 56 Mins 4 Secs
== Masa and Varsha Nirnaya ==
Once we understand how the day is determined under each Mana - kind of measurement - we proceed to make the Masa (month) and Varsha (year) calculations in this section.
=== Saura Masa and Varsha ===
The time taken by the Sun to complete a revolution around the Earth, as observed from the Earth, is defined as a Saura Varsha (Solar Year)
== Four Other Manas ==
=== पितृमानम् ॥ Pitr Mana ===
<blockquote>त्रिम्शता तिथिभिर्मासश्चान्द्रः पित्र्यमहः स्मृतम्। निशा च मासपक्षान्ते तयोर्मध्ये विभागतः॥ (Sury. Siddh. 14.14)<ref name=":0" /></blockquote>Thirty tithis make a lunar month (mentioned under Tithis) which constitutes one day and night for the Pitrs. The end of Chandramasa (lunar month) i.e., the end of the New moon day (Amavasya) corresponds to the noon time for the Pitrs and the end of the Full moon day (Purnima) corresponds to the midnight time for the Pitrs. Thus the middle of Shukla Ashtami tithi corresponds to the start of the day for Pitrs and the middle of Krshna Ashtami tithi corresponds to the start of the night for the Pitrs.<ref name=":2" /> The Bhugola Adhyaya of Surya Siddhanta further discusses this topic establishing Amavasya as the noon time and Purnima as midnight for Pitrloka (Page 767-768 of Reference<ref name=":1" />).
==== Purpose of Pitr Mana ====
# Determine the Masikas (performing monthly Pitr kriyas upto one year of death).
# Determine the time of annual Shraddha
== References ==
== References ==
[[Category:Vedangas]]
[[Category:Vedangas]]
<references />