Modern and Vedic astronomy was born through man's first attempts to measure the passage of
time by observing motions of Sun and the Moon. Thus, time reckoning is synonymous with astronomy even today.
While modern method of time reckoning has changed over the years, Vedic methods remain unchanged
as people continue to celebrate Ram Navami, Krishna Janmashtami etc as per
Hindu calendar since Vedic days. This article presents different process of time reckoning and
their significance in our daily life.Modern
The moment we think of measurement of time, most of us recollect either grandfather's clock or
our first Physics pendulum experiment using string and mass during school days.
We also know how to adjust the period of this pendulum by increasing or decreasing its
length. Yet another factor control this period is the earth's gravity while mass of the pendulum has no effect.
This mechanical clock when synchronized with the mean solar time, it gives us the time on 24-hour basis.
The mean solar time can be defined as a mean Sun which moves eastward along the celestial equator at average rate of true Sun.
Greenwich Mean time(GMT) or Universal Time(UT) is simply a mean solar time measured from Greenwich,
England and used in navigation and surveying for hundreds of years. Each country adopts its standard time based on
standard meridian with respect to Greenwich. Though look simple, what if earth does not spin in its axis at
uniform and constant rate? Well, there is a problem, Earth loses about 45 to 50 seconds in one century and in one
millennium, the planet is 1.25 hours behind expected time schedule. Therefore, a better standard for the
absolute measurement of time is the use of solar system dynamics. The orbital motions of the planets and of
the moon are predictable to very high accuracy and are directly verifiable through observations.
The resulting time is referred to as Ephemeris Time (ET).
The Ephemeris time remained the basis of all time measurements until 1984.
Then with the technological development, the complexity of celestial mechanics is now over
with the advent of atomic clock. The atomic or SI second is defined as 9,192,631,770 periods
of radiation corresponding to the transition between two hyperfine levels (F=4 to F=3) of
the ground state of the Cesium 133 atom. The SI second was carefully chosen to agree as
closely as possible to be ephemeris second. Thus in 1984, SI second was adopted as the
newest time standard and Terrestrial Dynamic Time (TDT) replaced Ephemeris Time.
The accuracy of this atomic time is about 10-12. Currently, all electronic and computer
clocks are calibrated with respect to this atomic clock and become independent of celestial
system of time reckoning.
Today's calendar in its earliest form was based on the lunar cycle originated from the
Romans. Each month had one lunar cycle and 12 such months in a year accounting for
354 days. To keep the year synchronized with the seasons, a leap month had to be added
every other year. This is very much similar to the one adopted by Vedic calendar even
today. This was later reformed by Julius Caesar in 46 BC and accordingly the year had
365 days and a leap day was added every fourth year. Thus, average length of a Julian
year was 365 days and 6 hour but the tropical year (Sun returns to vernal equinox) is 11m
14s shorter. Consequently, after 128 year the Julian year start almost 1 day too late.
In 1582, the difference was about 10 days and Pope Gregarious XIII reformed the calendar
again and known as Gregorian calendar that we continue to follow even today.
He made few exceptions for the leap year such as; the years divisible by 100 are not
leap years except when it is divisible by 400. That is why year 2000 was a leap year. Vedic
The word "Jyotishya" in the Vedic literature connotes "Astronomy" which was recognized as
the foremost of the six auxiliaries of Veda. The Vedic life (1000 B.C. to 400 B.C.)
was noted for the performance of several rituals and sacrifices at prescribed times to
satisfy heaven and God. Vedanga Jyotishya was the earliest of all Vedic text on astronomy
and was an integrated part of the life of the Vedic people of whom Vedic priests were well
versed. Accordingly, a civil day was divided in to 30 muhurthas, 1 muhurtha in to 2
nadikas i.e., 60 nadikas (Ghati) for a day. The text also mention 27 nakshatras* and
tithis (longitudinal difference between Sun and Moon in steps of 12 degrees). The Moon covers
360 degree from new moon to new moon accounted for 30 tithis in a lunar month. A month was
divided in two parts or pakshas, the bright half (Shukla paksha) and the dark half
(Krishna paksha). A tithi that is current upon Sunrise is tithi of the day.
Thus a day is reckoned from Sunrise to Sunrise and time is reckoned in nadies or ghaties
and in their fractions (1ghati = 24 minutes) from Sunrise. Names of the lunar months**
were given based on the nakshatra in which the full moon occurred. For example, during
Chaitra month, Moon will be in or closer to Chitta nakshatra during full moon.
Similarly, 12 solar months were also identified and when two new moons occur in a given
solar month, the lunar month is reckoned as additional month thus correcting the difference
between solar year and lunar year.
The first point of the nakshatra Ashwini (near the star zeta) is the first point from
which the longitude is measured. All the planets are supposed to have zero longitude
(first point Ashwini) at the beginning of the maha-yuga. The beginning of current Kaliyuga
is an epoch, which is presumed to have commenced on the midnight between February 17 and 18,
3102 B.C. The number of civil days elapsed from a given epoch is known as ahargana.
This is the basis for computation of all planetary positions in traditional almanac.
A solar year is reckoned from Saka era (78 AD) in the south and Vikrama era (57 B.C.)
in the north whenever Sun transit over Ashwini. Similarly, a lunar year (samvatsara) is
reckoned whenever a new moon occurs in or close to Ashwini after the end of month Phalguni.
This is how and when we celebrate Sauraman and Chandraman yugadi respectively as a
Hindu new-year day. A cycle of 60 lunar years has been given names (Prabhava, Vibhava .etc)
and this cycle repeats. For example, the lunar year Tarana in 2004-2005
will repeat again after 60 years in 2064. Thus according to Vedic literature a full human life is considered to be 120 years comprises of two such cycle. This is the total number of years accounted under Vimshottary dasha system.
Vendanga-jyotishya is in the form of various sutra, a style noted for its depth of
contents continue to be in use for a long time until the invasion of India by Alexander
the Great in fourth century B.C. After Greco-Roman contacts with India, a new class of
astronomical literatures called siddhantas started emerging. An important development in
this literature was the gradual replacement of nakshatra system by 12 signs of the zodiac,
Mesha, Vrishabha, Mithuna..Meena, similar to the animistic notations of the Babylonians and
Greeks. Accordingly, 27 nakshatras consisting of 108 parts (27x4) divided by 12 gives 9
parts for each sign. Thus, Mesha made up of Ashwini, Bharani and 1 part of Kritika
(4+4+1=9) and so on. In addition, name of the solar months was identified with the
respective sign. A few centuries after Christian era Indian astronomers developed new
mathematical tools and methods for promoting astronomical calculations. Spherical
trigonometry is one such area developed side by side with algebra and geometry added
veneer of accuracy to the study of several astronomical phenomena. Thus newly emerging
siddhantas were set of rules (including thumb rules) arriving at solutions to the complex
astronomical problems. Among the 18 siddhantas Varahamihira, the great grand master of
astronomy as well as astrology, ably codified Saura (Surya), Paitamaha, Vasistha,
Romaka and Paulisa during 505 A.D. He reiterated that Surya siddhanta was the most
accurate of all and became the basis of many traditional almanacs published even today
from various parts of India. Surya siddhanta in the current form has no human authorship
associated with it but, represents contribution from several noted astronomers over the
years. Significance
We all well versed with modern time keeping to the extent that most of us maintain
hourly/daily/weekly/monthly log or schedule of activities with the help of computers
since it has direct economic significance in our daily life. In the absence of modern
time keeping systems, the almanacs (Vedic) were the only reliable and consistent
timekeepers of all past events that enable people to celebrate and enjoy all traditional
feast and festivals even to this date. Most important of all, living in harmony with the
nature was the key to the successful, peaceful and happy life during Vedic days.
Every species in this earth follows certain hidden rule of the nature in creation,
development and destruction with respect to time. Biological make up all species
should be in harmony with the nature during its entire development process. However,
when ever this process goes out of balance or become arrhythmic the misery strikes.
By nature, humans tend to go arrhythmic more often than other species, with the result
encounter more challenges in every walk of life. Vedic people had solutions to such
problems and came up with muhurthas (Auspicious time) for all major activities that
can be found in any almanac for guidance, a tradition continuing even to this day.
A logical extension of this gave rise to the evolution of Astrology (300 B.C to 500 AD)
that formulated effect of different celestial objects and their movements upon an
individual right from cradle to grave. In India, Ayurveda and Jyothishya (Astrology) go hand in hand while treating patient in the past. The physician checks pulses at different places and then try to ascertain patient's rhythmic cycle through astrology to come up with right treatment. The scientific reasoning for this is human species undergoes three different cycles from time of birth known as biorhythm. They run simultaneously in a cyclic manner with periodicity given as follows.
* 27 Nakshatras: 1.Ashwini; 2.Bharani; 3.Kritika;
4.Rohini; 5.Mrigasira; 6.Ardra; 7.Punervasu; 8.Pushya; 9.Ashlesha; 10.Magha;
11.Hubba; 12.Uttara; 13.Hasta; 14.Chitta; 15.Swathi;16.Vishakha; 17.Anuradha;
18.Jeshta; 19.Moola; 20.Poorva Ashada; 21.Uttara Ashada; 22.Shravana; 23.Dhanishta;
24.Shatabhisha; 25.Poorva Bhadra; 26.Uttara Bhadra; 27.Revathi. **Lunar months: 1. Chaitra (Mar-Apr); 2. Vaishakha
(Apr-May); 3. Jyeshta (May-Jun); 4.Ashada (Jun-July); 5.Shravana (Jul-Aug);
6.Bhadrapada (Aug-Sep); 7.Ashwija (Sep-Oct); 8.Kartika (Oct-Nov);
9.Margasira(Nov-Dec); 10.Pushya (Dec-Jan); 11.Magh (Jan-Feb); 12.Phalguni (Feb-Mar). copyright (c) 2000 MyAstro |