Barring few with gray hairs almost everyone has discarded the Indian calendar system. Not because it is worthless but so difficult to understand for IQ challenged era.
Seems illogical that in Indian calendar suddenly one date just disappears; after 5th you enter into 7th ridiculous. This drove me to write something for convent educated folks. Indian spiritual science maintains time does not exists in their experience for rest of the people it exists with full force and tangibly true. Lets go.
From the earth’s frame of reference Sun and moon moves in circle that is sky 360 degree divided by 12 comes 30 degree portions known as constellations.
A solar year is either the time it takes from one vernal equinox to the next (365.242) days known as tropical year or the time taken by sun to cover all 12 constellations known as sidereal year (365.256)days. Rest you know the leap year concept to adjust the after decimal numbers.
A Lunar month is either the time taken by it to travel all 12 constellations (27.3217 days) known as sidereal month or the time between one full moon to another (29.5306) days known as synodic month.
To have a sync between two Indian calander does not go by leap year rather introduced “intercalary Month” which may come after every two and two third year. The interesting part is how do they find the date or tithi? It is done in three noteworthy steps.
A-Calculate the difference between longitude of Sun and Moon
B-Divide the distance by 12 degree and drop the remainder.
C-The quotient plus 1 shall be the number of the date, If it is more than 15 subtract 15 from this.
So we have only date range from 1 to 15 but in two sets i.e Full moon and new moon. Aghast!