Use of tropical year
- None of the calendar systems currently in use around the world perfectly reflect the length of a tropical year.
- Julius Caesar’s Julian calendar was 365 days long, but added a leap day every 4 years. Year started in January, month honoring the two faced God Janus looking back and forth in time.
- Gregorian calendar was same as Julian calendar - but removing 1 leap day addition every 100 years. Because a common year has 365 days in today’s Gregorian calendar, a leap day is added to bring it in sync with the tropical year.
- Accounting for periodic adjustments, its error is 27 sec/year (1 day in 3236 years).
- Persian Al Hijri calendar is the most accurate. Accounting for periodic adjustments, its error is less than 1 sec/year (1 day in 110,000 years).
- राशिनिर्णये होरे च सौरराशिम् अवेक्षन्ते पाश्चात्याः। “Western astrology uses the so-called tropical zodiac in which 0 Aries is defined by the vernal point (the celestial point where the sun stands at the beginning of spring). The tropical zodiac is a division of the ecliptic into 12 equal-sized zodiac signs of 30° each. Astrologers call these signs after constellations that are found along the ecliptic, although they are actually independent of these constellations. Due to the precession of the equinox, the vernal point and tropical Aries move through all constellations along the ecliptic, staying for roughly 2160 years in each one of them. Currently, the beginning of tropical Aries is located in the constellation of Pisces.” [SW]
- Assymetry in SB altar construction (and much later Ankor Wat design) represents division of year’s seasons in 4000BC (“Date of Solar orbit of Satapatha BrahmaNa” - Chandra Hari अत्र।)
- “It was the Indian astronomy historian S. B. Dixit (also written Dikshit), who first proposed in 1896 that the zodiac should be oriented towards the star Spica (Citra in Sanskrti), in his important work History of Indian Astronomy (= Bharatiya Jyotih Shastra; bibliographical details further below). Dixit arrived at the conclusion that, given the prominence that Vedic religion gave to the cardinal points of the tropical year, the Indian calendar should be reformed and no longer be calculated relative to the sidereal, but to the tropical zodiac. " [SW]
- Also see tropicalization parts of this page.
Year length
- Via MT: “From the early times the Arya knew of the year being approximately 365 days– the sAmidhenI hymns contain 360 syllables in the form of 15 gAyatrI-s + the oM bhurbhuvasvaroM forming the year by supplying the remaining days and its fraction. Two great vedic shrauta masters, the pa
nchAla prince babara prAvAhaNi and sArvaseni shaucheya declare the logic behind the pancharAtra sacrifice. They say that the year which is the ya~jna is complete only by adding the 5 days. They say that 4 days is too few while 6 days is two many so to complete the year we add 5 last days to the year . This is how the 365 day approximate year is laid out (TS 7.1.10). Right in the R^igveda the shunaHshepa, the son of ajigarta notes that the intercalary month is used to correct for the imperfect match of the lunar and solar years (RV1.25.8).”
National tropical / sAyana calendar
The calendar known as ‘National Calendar’ was introduced by the Govt. of India with effect from 22 March 1957, corresponding to the 1st day of the year of this calendar which was 1 Chaitra 1879 Saka Era. Report excerpts here.