Astrology API accuracy

How we test accuracy

• Reference values were worked out on their own with Swiss Ephemeris, a widely used standard for astrology software, and are treated as the right answer.
• The ayanamsa is checked on 8 dates across two centuries. Planets and the rising sign are checked on one test chart: New Delhi at noon on Aug 22, 2026, India time.
• Each limit is the largest difference found, plus the rounding in the reference values, rounded up. The tests fail if a result ever drifts past a limit.
• Two of the tests exist because of real bugs we found and fixed: a missing correction that moved every planet by about 10 arc seconds, and an error that moved only the rising sign. Both are now tested directly.
• Rahu and Ketu are not part of the planet check.

Other checks

• Dasha periods add up to 120 years, and every sub-period fits its parent period exactly, date for date.
• The panchang parts (tithi, yoga, karana) stay in their valid ranges for any position of the Sun and Moon.
• Coordinates in a local number format, such as 40,7128, are read correctly, and unclear or out-of-range ones are refused.
• Fasting-day dates were compared with Drik Panchang, a widely used published calendar: 495 of 496 dates for New Delhi (2026 to 2028) and Beijing (2026) matched.

Where the classical texts disagree, the rulebook states which choice the API follows.