
                  The Vaisnava Calendar Program
                          Version 4.01
                         


                  Written by Shyamasundara Dasa
                    and Markandeya Rishi Dasa



copyright (c) The Bhaktivedanta Book Trust International, Inc.
1983-1999. All rights reserved.





Contents
--------

 1. Where to obtain VCAL
 2. VCAL is freeware
 3. List of files
 4. Spellings
 5. Introduction to the program
 6. How to use the program
 7. Some basic Vedic astronomy
    a. The movements of the moon and sun
    b. The definitions of solar and lunar months and years
        i. The solar month and year
       ii. The lunar month and year
 8. The Pancanga, or the Vedic calendar
    a. Tithi
    b. Naksatra
    c. Yoga
 9. Reasons to follow a lunar calendar
10. Traditional and modern methods of calculation
11. Some comments on interpreting the Vaisnava calendar
    a. Names of years and months
    b. When to observe Ekadasi
    c. "Break fast 05:18 - 09:34" and "Daylight-savings not 
       considered"
    d. Double or no tithi
    e. Sankranti
    f. Names for the signs of the zodiac
12. Parting Words


1. Where to obtain VCAL
-----------------------

The most recent version of VCAL should be available on the
Worldwide Web at <http://www.iskcon.org/calendar/>.


2. VCAL is freeware
-------------------

The Bhaktivedanta Book Trust International owns the program,
but you are welcome to use it and share it with others. There
are only a few rules. They appear in the file LICENSE.TXT.


3. List of files
----------------

The following files are included in this archive:

VCAL.EXE      Main program
VCAL.OV1      Overlay used by the main program
VCAL.OV2      Overlay used by the main program
VCAL.OV3      Overlay used by the main program
VCAL.TOW      File containing list of towns
VCAL.HLP      Help file
DOC-VCAL.TXT  The document you are now reading
HISTORY.TXT   Describing changes in each new version.
QA401.TXT     Questions and Answers for the release of this
              version.
LICENSE.TXT   Your license for the free use of this program
FESTIVAL.TXT  About the festivals mentioned in the calendar
PERSONS.TXT   About the saints and incarnations mentioned in
              the calendar 
PRABHPAD.TXT  About His Divine Grace A.C. Bhaktivedanta Swami
              Prabhupada
BBT.TXT       About the Bhaktivedanta Book Trust
FILE_ID.DIZ   Brief identification of this program


You are welcome to share VCAL with others, but please
distribute the complete archive, not just selected files.


4. Spellings
------------

To spell Sanskrit (and Bengali) names and terms, VCAL uses 
"as-if-diacritical" spellings. That is, it spells as if it 
were employing the diacritical marks used by scholars, but 
leaves those marks out. Thus "Krishna" is spelled "Krsna." The 
VCAL documentation follows the same system. A guide to the 
Sanskrit transliteration system is found in all the books 
of the Bhaktivedanta Book Trust. 



5. Introduction to the program
------------------------------

VCAL calculates Vedic lunar calendars. There are different ways
to make calendars according to the Vedic lunar system, all very
similar. This program makes the calendar according to the
Gaudiya Vaisnava tradition, an important branch of the Vaisnava
tradition. The word "Vaisnava" denotes a worshiper of Visnu.

VCAL has been developed for ISKCON, the International Society
for Krishna Consciousness, which follows the Gaudiya Vaisnava
tradition. But the calendars VCAL produces should be useful for
most people who follow a Vedic lunar calendar.

VCAL was written by Syamasundara Dasa. He and Markandeya Rsi
Dasa developed it further.

To develop the program, in June 1989 Markandeya went to India
for extensive research and consultation with persons
knowledgeable about calendar making, astronomy, and Vaisnava
observances. The learning and expertise of those consulted have
contributed greatly to the reliability of this program.


6. How to use the program
-------------------------

VCAL runs under DOS. It is not a Windows program. To install
it, simply place all its files in any directory. To uninstall
it, simply erase the files. 

The program is easy to use, with a simple menu system. The F1
key gives you context-sensitive help.

VCAL uses a list of towns for which it can calculate a
calendar.  You may enter new towns as needed, to a limit of
1200. If you need more, you must delete some towns you don't
use. (Or you can keep more than one town file and switch between
your files by renaming them.)

Latitudes greater than 65 degrees and 35 minutes (north or
south) cause problems for VCAL. Using such latitudes may result
in wrong calculations or may terminate the program with an error.

If you add new towns to the list, take care to enter the
latitude, longitude and time zone correctly. If any of this
information is wrong, your calendar will be incorrect. (If you
give your modified town files to others, this warning is even
more important.)

VCAL also provides for "batch files," which allow you to
calculate several calendars at a time. When you choose, from the
Main Menu, "Make Vaisnava Calendar," you will be asked, two
screens later, whether you want to calculate the calendar for
only one town or for many. If you choose "many," VCAL will
present you a list of the available batch files. Each batch file
allows you to calculate calendars for many towns through one
command. 

You can also use VCAL to calculate birthdays. Insert the birth
information according to the Western calendar, and VCAL will
tell you the corresponding Vedic day of birth.

As of 1999, VCAL has been used for about twelve years, but
could of course still have bugs. If you find a suspected bug,
please contact Markandeya Rsi Dasa at this e-mail address:
<markandeya@geocities.com>.


7. Some basic astronomy
-----------------------

   a. The movements of the moon and sun
   ------------------------------------

From the perspective of an observer on earth, the sun and moon
and stars are moving around the earth every day. If we look at
the sky at night, as the hours pass we will see the moon and
stars gradually move west across the sky, seeming to move
together. But as several nights go by, we may notice that the
position of the moon in relation to the stars moves towards the
east.

The extent of this relative movement comes to roughly 13
degrees per day. Thus the moon will complete a full rotation
through the belt of stars, called the zodiac, in about one month.

A similar situation is true for the sun. Because the stars are
too weak to be seen during the day, we cannot see the sun and
the stars simultaneously. But if we could, we would see the sun
moving gradually against the background of the stars. The sun,
however, moves more slowly than the moon -- only about 1 degree
each day. So we would have to wait longer to observe the
difference. For the sun to come back to the same group of stars
on the zodiac takes one year.


   b. The definitions of solar and lunar months and years
   ------------------------------------------------------

One can define a month and a year in two basic ways: by the
movement of the moon and by the movement of the sun.


      i. The solar month and year
      ---------------------------

The Vedic solar month lasts the time it takes for the sun to
traverse a complete sign of the zodiac. The zodiac has twelve
signs, so each sign covers an angle of 30 degrees. Because the
sun moves across the zodiac by about 1 degree each day, to
traverse a complete sign takes about 30 days -- more exactly,
30.4 days. Twelve such months make one solar year -- that is, a
little more than 365 days. In other words, a solar year is the
time it takes for the sun to start from any group of stars and
return to it. Such a year stays synchronized with the seasons.


      ii. The lunar month and year
      ----------------------------

The lunar month and year are slightly more complex. The Vedic
calendar defines the lunar month in terms of the phases of the
moon. We know that the phases of the moon change. The moon is
sometimes full, sometimes half, and sometimes new, depending on
how much of the moon we on earth can see lit up by the sun. When
the sun and moon are close to one another on the zodiac, the
side of the moon illuminated by the sun will mainly have its
back to us. So we will see only a sliver, and most of the moon
will seem dark. Then again, when the sun and moon are on
opposite sides of the zodiac, the side of the moon we see from
earth will be fully illuminated, so we will see a full moon. All
other positions of the sun and moon result in the other,
intermediate lunar phases.

In the Vaisnava calendar a month starts the day after one full
moon and continues through the next full moon. This takes about
29.5 days.

Just as 12 solar months make one solar year, 12 lunar months
make one lunar year. Since one lunar month takes 29.5 days, 12
such months will take about 12 times that long -- that is, 354
days.

This lunar year is 11 days shorter than the 365-day solar year,
so  although the month synchronizes with the lunar phases, the
year does not synchronize with the seasons. Counting by the
solar calendar, every solar year the lunar year will begin 11
days earlier. So, to synchronize the lunar year with the
seasons, the Vedic calendar adds an extra month about every
third year, according to certain rules. In this way the lunar
and solar years stay in synch.


8. The Pancanga, or the Vedic calendar
--------------------------------------

The Vedic calendar is called Pancanga. The word Pancanga
indicates that the calendar consists of five parts, or tells
about five elements. These elements are vara (the day of the
week), tithi (the lunar day, or phase of the moon), karana (half
a tithi), naksatra (the position of the moon in the zodiac), and
yoga (a measurement derived from the positions of the sun and
moon). For normal use of the calendar, one need not understand
all these elements. But some of them are described as follows. 


   a. Tithi
   --------

As we have discussed, the lunar month marks the time from one
full moon to the next. The lunar month is divided into 30 parts,
called lunar days, or tithis. The tithis are simply the
different phases of the moon. Thus the first tithi starts at the
moment when the moon is full -- that is, when the angle between
the moon and the sun is 180 degrees and it continues until
the angle has increased 12 degrees. Then, that much less of the
moon seems bright to us: the moon is no longer completely full.

Now the second tithi starts, and it continues until the angle
between the sun and moon has increased 12 degrees more. Slightly
more of the bright side of the moon now has its back to us, and
so the moon is even less full. 

When 15 such tithis have passed, the angle between the sun and
the moon has increased by 180 degrees. This time the bright side
of the moon cannot be seen at all, and so we have a new moon.
Then 15 more tithis gradually pass, and the moon again becomes
full. When 30 tithis have thus passed, the month ends.

The period when the moon wanes, or decreases in size, is called
krsna paksa ("the dark fortnight"), and the period when it
waxes, or increases, is called sukla paksa or gaura paksa ("the
bright fortnight"). The words Krsna and Gaura used here are
specific to the Gaudiya Vaisnava tradition.

Some lunar calendars start the month from the 0-degree position
-- that is, directly after the new moon. Such calendars are
called mukhya candra. Other calendars, such as the one used by
the Gaudiya Vaisnavas, start directly after the full moon, with
the Krsna paksa. Such calendars are called gauna candra.

Except for the new moon and the full moon, the names of the
tithis are simply counting words: pratipat, dvitiya, trtiya
(first, second, third), etc. These names are the same for the
tithis occurring during Krsna paksa (the dark period of the
moon) and the gaura paksa (the bright period). The new moon is
called amavasya, and the full moon purnima.


Krsna paksa                         Gaura paksa
Tithi   Name                        Tithi   Name

  1   Pratipat                       1   Pratipat
  2   Dvitiya                        2   Dvitiya
  3   Trtiya                         3   Trtiya
  4   Caturthi                       4   Caturthi
  5   Pancami                        5   Pancami
  6   Sasti                          6   Sasti
  7   Saptami                        7   Saptami
  8   Astami                         8   Astami
  9   Navami                         9   Navami
 10   Dasami                        10   Dasami
 11   Ekadasi                       11   Ekadasi
 12   Dvadasi                       12   Dvadasi
 13   Trayodasi                     13   Trayodasi
 14   Caturdasi                     14   Caturdasi
 15   Amavasya (new moon)           15   Purnima (full moon)

Because the speed of the moon in relation to that of the sun is
not constant but varies, a tithi is not a fixed duration of
time. Its length fluctuates between 19 and 26 hours. Therefore,
since a lunar tithi does not correspond to the 24-hour solar
day, a tithi may start at any time of the day.

There are certain tithis on which the followers of the Vedic
culture follow various observances or celebrations. On what day
is such a tithi to be observed? The general rule is that one
will celebrate a tithi on that day whose sunrise falls within
the tithi, though sometimes other rules come into effect.

The Ekadasi tithi is especially important, and special rules
determine when to observe Ekadasi. Special rules also sometimes
apply for festivals such as Sri Krsna Janmastami.


   b. Naksatra
   -----------

As previously mentioned, in the sky the belt of stars called
the zodiac is divided into 12 signs, which cover 30 degrees
each. There is also a way of dividing the zodiac into 27 parts,
which cover 13-1/3 degrees each. These parts are called
naksatras.

While moving over the zodiac, the moon continuously passes
through these naksatras one by one. In the Vedic calendar,
naksatra simply refers to the naksatra within which the moon is
present at sunrise on any particular day.


   c. Yoga
   -------

Tithis and naksatras can easily be understood in relation to
the phenomena in the sky. Tithi is the phase of the moon, and
naksatra marks the position of the moon. But yoga is not easily
understood in a similar way. The yoga is determined by adding
the angle or longitude of the sun and moon, reducing the sum to
fit in the circle of 360 degrees (by subtracting 360 degrees if
needed), and then dividing the resultant number by 13-1/3
degrees. Like the naksatras, the yogas are also 27 in number.


9. Reasons to follow a lunar calendar
-------------------------------------

In the Vaisnava calendar the times for various celebrations are
determined by the tithi, sometimes with naksatra and other
elements of the calendar taken into account.

Most scholars who have analyzed the old Indian calendar
systems, both lunar and solar, have concluded that the lunar
system is the more ancient.

The lunar phases are known to influence agriculture, and
according to scriptures like Manu-samhita (The Law of Manu) they
also influence more subtle aspects of human life.


10. Traditional and modern methods of calculation
-------------------------------------------------

Traditionally the astronomical calculations needed to make a
Pancanga were done according to one of the astronomical texts
such as Surya Siddhanta. The methods described in Surya
Siddhanta are basically quite similar to modern astronomical
methods for ascertaining the positions of the planets. The main
difference is that Surya Siddhanta has a simpler model. Such a
model is needed if the calculations are to be done by hand in a
practical way.

The methods of Surya Siddhanta could be used by a skillful
person at any time, without the need for modern equipment. All
that was needed were some observatory instruments that could be
built without high technology. These instruments were used
regularly to check that the calculations tallied with observable
reality. When a difference appeared after some time, corrections
were made to the astronomical constants in the formulas. With
this system, fairly good results were obtainable even though the
astronomical model was simple. Its accuracy cannot be compared
to that obtained by modern methods, but for the purpose of
astrology and creation of calendars it sufficed.

This computer program uses formulas that give an accuracy of 1
minute of arc for the longitude of the sun and 2 minutes of arc
for the longitude of the moon. When determining ending times of
tithis these errors can result in a maximum error of 5 minutes
of time. The average error is about 3 minutes. Such an error
will report an Ekadasi (the eleventh tithi) on the wrong date
roughly once every 20 years.


11. Some comments on interpreting the Vaisnava calendar
-------------------------------------------------------


   a. Names of years and months
   ----------------------------

Following Gaudiya Vaisnava tradition, the years are counted
from the appearance of Lord Sri Krsna's incarnation as Lord Sri
Caitanya Mahaprabhu. Lord Caitanya is also known as Gaura, so
the year is called "Gaurabda," "the year of Lord Caitanya."

Each month, or "masa," is known by a name of Visnu. The months,
the Sanskrit names by which they are commonly known in India,
and their rough equivalents according to the Gregorian calendar
are listed as follows:



1.  Visnu             Caitra          March-April              

2.  Madhusudana       Vaisakha        April-May                

3.  Trivikrama        Jyestha         May-June                
 
4.  Vamana            Asadha          June-July                

5.  Sridhara          Sravana         July-August             

6.  Hrsikesa          Bhadrapada      August-September         

7.  Padmanabha        Asvina          September-October        

8.  Damodara          Kartika         October-November         

9.  Kesava            Margasirsa      November-December       

10. Narayana          Pausa           December-January         

11. Madhava           Magha           January-February 
        
12. Govinda           Phalguna        February-March           

   Purusottama        adhika,         intercalary month
                      or Dvitiya 
                      Jyestha


   b. When to observe Ekadasi
   ---------------------------

Ekadasi, the eleventh tithi, has special importance. In the
scripture Caitanya-caritamrta (Madhya-lila, chapter 24), Lord
Caitanya Mahaprabhu instructs Sanatana Gosvami regarding the
Vaisnava regulative principles. In text 342 Lord Caitanya says:

"You should recommend the avoidance of mixed [viddha] Ekadasi
and the performance of pure Ekadasi. You should also describe
the fault in not observing this. One should be very careful as
far as these items are concerned. If one is not careful, one
will be negligent in executing devotional service."

As described in the book Hari Bhakti Vilasa, viddha (mixed)
Ekadasi takes place when the eleventh tithi starts before
sunrise but the tenth tithi still presides at the beginning of
brahma muhurta (the auspicious period that starts an hour and a
half before sunrise).

On Ekadasi it is traditional to fast. But under certain
conditions, called mahadvadasi, one fasts not on the Ekadasi but
on the next day, the dvadasi, even though the Ekadasi is suddha,
or pure, and not viddha, or mixed. There are eight mahadvadasis.

The calendars produced by this program make it easy to see when
to observe Ekadasi. The Ekadasi fast should be observed on the
day called suddha (pure) Ekadasi, or alternatively on
Mahadvadasi, even if the previous day is called Ekadasi. All
this is clarified by the asterisk (*), which indicates a fast,
at the right margin of the calendar.


   c. "Break fast 05:18 - 09:34" and "Daylight-savings not considered"
   -------------------------------------------------------------------

To complete the proper observance of Ekadasi, the next morning
one should end the fast after the first time given in the
calendar and before the second time. The calendar gives these
times according to the standard time of the place for which the
calendar is made. 

During the summer, many locations do not follow standard time,
but instead move their clocks an hour ahead (or sometimes more)
to make more use of the hours of daylight. So, for example, 5
o'clock in the morning becomes 6 o'clock instead. The Vedic
Calendar program does not take such daylight-saving time into
account. So for days when your location uses daylight-saving
time, you must adjust the times given by the calendar.
Generally, this means that when daylight-saving time is in
effect you should add an hour to the times given.


   d. Double or no tithi
   ---------------------

When studying the calendar, you may find that sometimes a tithi
is skipped and sometimes one tithi comes on two consecutive
days. There is nothing wrong with this. For each day, the
calendar just shows which tithi (moon phase) prevails at the
time of sunrise. Sometimes a given lunar phase may begin after
one sunrise and end before the next, and therefore on the
calendar that tithi appears missing. Or sometimes one lunar
phase extends throughout two sunrises in a row, and therefore
that tithi appears twice.

A person's birthday is determined by the tithi prevailing at
the moment the person was born. Every year thereafter, the day
to celebrate as the birthday should be the day whose sunrise
occurs during that same tithi. If the tithi prevails on two
consecutive sunrises, the sunrise that has the same naksatra as
at birth will be the proper day for celebration. If neither
sunrise occurs with that naksatra, then the latter of the two
days should be chosen. If there is no day whose sunrise occurs
during that particular tithi, then the day within which the
tithi falls should be chosen as the day of celebration.

Suppose, for example, that a person's appearance day should be
celebrated on dvitiya tithi in the month of Kesava and that for
the month of Kesava the calendar lists two dvitiya tithis, one
after another. And suppose that the naksatra that prevailed at
birth is not present. Then the second dvitiya should be chosen
as the day of celebration. If the calendar shows no dvitiya at
all, then the appearance day should be celebrated on the day
listed as pratipat, because the dvitiya phase of the moon will
occur during that day.


   e. Sankranti
   ------------

Sankranti means the time when the sun enters a sign of the
zodiac. If you are conversant with astrology, you might wonder
why the calendar shows the sun entering the various signs of the
zodiac at times different from those given in Western astrology.
This is one of the differences between the two kinds of
astrology, Western and Vedic. The difference pertains to a
certain angle called ayanamsa, which is presently around 23
degrees. The explanation of ayanamsa can be found in books about
Vedic astrology.


   f. Names for the signs of the zodiac
   ------------------------------------

Here are the Sanskrit names for the signs of the zodiac,
alongside their English counterparts.


SANSKRIT       ENGLISH


1. Mesa        Aries

2. Vrsabha     Taurus

3. Mithuna     Gemini

4. Kataka      Cancer

5. Simha       Leo

6. Kanya       Virgo

7. Tula        Libra

8. Vrscika     Scorpio

9. Dhanus      Sagittarius

10. Makara     Capricorn

11. Kumbha     Aquarius

12. Mina       Pisces



12. Parting Words
-----------------

We wish you a life fulfilled with good Vaisnava years. Hare
Krsna.



Documentation (c) 1999 The Bhaktivedanta Book Trust
International, Inc. All rights reserved.

