In order to reconcile the lunar and solar years the Hindus hit upon
an ingenious device. It was ordained that any month in which the sun
did not enter a new sign of the zodiac would not count and would
be followed by another month of the same name. Thus in the month
of Chait the sun must enter the sign Mesha or Aries. If he does not
enter it during the lunar month there will be an intercalary Chait,
followed by the proper month of the same name during which the sun
will enter Mesha. [218] Such an intercalary month is called Adhika. An
intercalary month, obtained by having two successive lunar months
of the same name, occurs approximately once in three years, and by
this means the reckoning by twelve lunar months is adjusted to the
solar year. On the other hand, the sun very occasionally passes two
Sankrants or enters into two fresh signs during the lunar month. This
is rendered possible by the fact that the time occupied by the sun in
passing through different signs of the zodiac varies to some extent. It
is said that the zodiac was divided into twelve equal signs of 30°
each or 1° for each day, as at this period it was considered that the
year was 360 days. [219] Possibly in adjusting the signs to 365 odd
days some alterations may have been made in their length, or errors
discovered. At any rate, whatever may be the reason, the length of
the sun's periods in the signs, or of the solar months, varies from
31 days 14 hours to 29 days 8 hours. Three of the months are less
than the lunar month, and hence it is possible that two Sankrants or
passages of the sun into a fresh sign may occasionally occur in the
same lunar month. When this happens, following the same rule as before,
the month to which the second Sankrant properly belongs, that is the
one following that in which two Sankrants occur, is called a Kshaya
or eliminated month and is omitted from the calendar. Intercalary
months occur generally in the 3rd, 5th, 8th, 11th, 14th, 16th and
18th years of a cycle of nineteen years, or seven times in nineteen
years. It is found that in each successive cycle only one or two
months are changed, so that the same month remains intercalary for
several cycles of nineteen years and then gives way generally to one
of the months preceding and rarely to the following month. Suppressed
months occur at intervals varying from 19 to 141 years, and in a year
when a suppressed month occurs there must always be one intercalary
month and not infrequently there are two. [220]
This method of adjusting the solar and lunar years, though clumsy,
is so far scientific that the solar and lunar years are made to
agree without any artificial intercalation of days. It has, however,
the great disadvantages of the frequent intercalary month, and also
of the fact that the lunar months begin on different dates in the
English solar calendar, varying by nearly twenty days.