According to the Indian calendar a Tithi is a lunar date, and is one of the five important aspects of
an Indian almanac (Panchang – Panch
means five and ang means parts). Most
of the Indian social and religious festivals are celebrated based on the tithi.
Until they left India and went overseas, the Indians didn’t really need to worry
about tithi to celebrate their festivals since a tithi in India almost invariably falls on the same day for the
entire region of India.
Even after migration to overseas countries, the Indians
living overseas would still celebrate their festivals on the same dates as
Indians in India would. For those
who would argue that behind these festival celebrations, it’s the faith, that
is more important than the date of celebration, I’m hundred percent with them.
However, the intention here is to provide information for those who want
to understand the importance behind the tithi
on which Indian festivals are based.
The calendar “date” that we are so familiar with in our
daily life is based on the solar calendar. The English calendar is a solar calendar.
The basis for the solar calendar is the rotation of the Earth around the Sun.
It takes the earth approximately 365 ¼ days to complete its rotation around
the Sun. The English calendar that most of us use today divides the 365 days of
earth’s period of rotation around the Sun in twelve months. The leap year, which occurs once every four years, accounts
for ¼ day per year.
Similar to the solar calendar a lunar calendar is also popular
and widely used in the Asian countries such as China, Pacific-rim countries,
Middle East countries, and India. The lunar
calendar, which is believed to have originated in India, has been around for a
very long time, even long before the solar calendar.
The lunar calendar is based on the moon’s rotation
around the Earth. The lunar month
corresponds to one complete rotation of the Moon around the Earth. Since this period of rotation of moon around the earth
varies, the duration of the lunar month also varies.
On average, the lunar month has about 29 ½ days.
In addition to moon’s rotation around the earth, the lunar year is
based on earth’s rotation around the Sun.
In general, the lunar year has twelve lunar months totaling to approximately 354
days, thus making the lunar year shorter by about 11 days than the solar year.
However, the lunar calendar accounts for this difference by adding an
extra lunar month about once every 2 ½ years.
The extra lunar month is commonly known as the “Adhik
Mas” in India (Adhik means extra
and the Mas means month).
The concept of this extra month is similar to the “Blue Moon” in the
West, which occurs almost about the same time with the same frequency of 2 ½ years.
The Indian lunar year begins on the new moon day that
occurs near the beginning of the Spring season. The twelve lunar months are:
As mentioned earlier, to account for the difference
between the solar and the lunar year an extra lunar month occurs about every 2 ½
years as the “Adhik Mas”.
According to the Moslem calendar which is widely followed
in Middle East and in other Moslem countries the lunar year is strictly based on
twelve lunar months of 354 days per year. That’s
why their holy month of Ramadan occurs
by approximately 11 to 12 days earlier than that in the preceding year.
The solar day (commonly referred as the "date” in
western calendar) has a fixed length of 24 hours. The change of date occurs at
midnight as per local time or standard time of a given local time zone.
Thus, the date changes from midnight to midnight.
Similarly the day (as in weekdays) changes from midnight to midnight as
per local or standard time for that location.
In other words, as per western (or English) calendar the length of day
and date is exactly 24 hours, and there is a definite correspondence between the
date and the corresponding day of the week.
A lunar day generally begins at sunrise, and the length of
lunar day is determined by the time elapsed between the successive sunrises.
As per Jewish calendar their lunar day begins at the sunset, and lasts
through the next sunset. A lunar
day is essentially the same as a weekday. In India the lunar day is commonly
referred as “War”. Just like
English calendar has seven days for a week, Indian calendar has seven wars
for a week. Thus,
English calendar weekdays
Indian calendar weekdays
The lunar date, however, varies approximately between 22
to 26 hours based on the angular rotation of the moon around the earth in its
elliptical orbit. In Indian
calendar, the lunar date is referred as “Tithi”.
The basis for the length of a lunar date is the angular distance between
the sun and the moon as seen from the earth.
As the moon rotates around the earth, the angular distance between the
sun and the moon as seen from the earth increases from 0 degrees to 360 degrees.
It takes one lunar month or about 29 ½ solar days for the angular
distance between the sun and the moon to change from 0 to 360 degrees. When the angular distance reaches zero, the next lunar month
begins. Thus, at the new moon a lunar month begins, at full moon, the angular
distance between the sun and the moon as seen from the earth becomes exactly 180
The lunar cycle begins with crescent moon, and the
crescent phase lasts till it culminates in the full moon, typically
lasting for about 15 days. Then the
moon enters in the waning phase until it disappears from the sky by lining up
with the Sun. The waning phase also
lasts for about 15 days. According
to the Indian lunar month, the crescent lunar phase fortnight is called as “Shudha or Shukla Paksha” and the waning phase of the lunar cycle
fortnight as “Wadya or Krushna Paksha”.
Thus, during Shudha (or Shukla) Paksha the angular distance between the moon and
the sun varies from 0 degrees to 180 degrees while that during the Wadya
(or Krushna) Paksha from 180 to 0 degrees.
If we divide 180 degrees into 15 equal parts, then each part becomes of
12 degrees in length. Thus, this
each twelve-degree portion of angular distance between the moon and the sun as
it appears from the earth is the lunar date or the Tithi.
Tithis or lunar dates in Shudha
(or Shukla) Paksha begin with Prathama
(first), Dwitiya (second), etc. till
we reach the Poornima, the lunar date
for the full moon day. Similarly for
the waning fortnight lunar cycle or Wadya
(or Krushna) Paksha, tithis begin
again with Prathama (first), Dwitiya
(second), etc. till we arrive Amavasya
or the day preceding the new moon. Thus,
when we refer to Ramnavami (the
birthday of Rama), it’s the Navami (ninth lunar day) of Shudha
Paksha of the lunar month Chaitra, or
Chaitra Shudha Navami. Similarly,
the Gokulashtmi (also called as
Janmashtami, the birthday of Krisha)
occurs on Shrawan Wadya Ashtami (eighth lunar day of Wadya Paksha of the lunar month Shrawan).
The angular velocity of the moon in its elliptical orbit
around the earth continuously varies as it is affected (according to Kepler’s
rule) by the relative distance between the earth and the moon, and also by the
earth’s relative distance from the sun. As
a result, the daily angular speed (the speed of the angle between the moon and
the sun as seen from the earth) varies somewhere between 10 to 14 degrees. Since
the length of a tithi corresponds to
12 such degrees, the length of a tithi
also varies accordingly. Therefore,
a tithi can extend over one day (24
hour period) or it can get skipped if two tithis
occur in one day.
Since the angular distance between the moon and the sun,
as referred here, is always relative to the entire earth, a lunar day or tithi
starts the same time everywhere in the world but not necessarily on the same
day. Thus, when a certain tithi starts
at 10:30 PM in India it also begins in New York at the same time, which is 12 PM
(EST) on the same day. Since the
length of a tithi can vary between 20
to 28 hours, its correspondence to a War
(a weekday) becomes little confusing.
As per the Indian calendar, the tithi for a given location on the earth depends on the angular
distance between the moon and the sun relative to the earth at the time of
sunrise at that location. Thus, for instance, assume on a November Monday the sunrise in New York city occurs
at 8:30 AM (EST).
Further assume that at 9 AM (EST) on the same Monday the angular distance between
the sun and moon is exactly 12 degrees just following the new moon of the Indian
lunar month Kartik. Since
the length of a tithi is 12 degrees, the tithi,
Kartik Shudha Dwitiya (second day) begins exactly at 9 AM on Monday of that
November in New York. However, at
the time of the sunrise on that Monday the tithi
Dwitiya has not begun. Therefore,
the tithi for that Monday for the city of
New York is Kartik Shudha Prathama
On the same Monday morning the sunrise in Los Angeles
occurs well past 9 AM (EST). Since
the tithi Dwitiya occurs everywhere in
the world at the same instant, therefore, for Los Angeles, the tithi for that Monday would be Kartik
For the same Monday at 9 AM (EST), it would be 7:30 PM in
Mumbai or in New Delhi. Thus, Tithi
for that Monday for the city of New York, Mumbai, and New Delhi is Kartik
Shudha Prathama (the first day of the Indian lunar month Kartik) while for the regions approximately west of Chicago and St. Louis,
the tithi for that Monday is Dwitiya. In other words, the tithi
Kartik Shudha Prathama for regions west of Chicago or St. Louis should occur
on the preceding day, the Sunday.
Prathama (the first day of the Indian lunar month Kartik) also happens to be the first day after Diwali. Most of the
Indians celebrate this as their New Year’s day. The Indians living in India,
Europe, and in the eastern part of the United States thus should celebrate their New
Year on that Monday while regions west of Chicago should on the preceding day,