---
type: Reference
bundle: jyotisha-kala
bundle_version: 0.12.0
id: surya-siddhanta
title: Sūrya Siddhānta
description: 'The most influential of the classical astronomical treatises: time divisions from truṭi to kalpa, mean and true planetary motions, eclipse computation, and the pañcāṅga quantities this bundle cites most.'
tags:
- reference
- surya-siddhanta
- astronomy
- ganita
timestamp: '2026-07-09'
okf_version: '0.2'
license: CC BY-SA 4.0
---

# Sūrya Siddhānta

The Sūrya Siddhānta, in its received form a text of the mid-first millennium CE with later revision, is the standard siddhānta of medieval Indian calendrics. Chapter 1 defines the ladder of time units (including the mūrta/amūrta distinction) and mean motions from epoch; chapter 2 derives true positions and the pañcāṅga quantities (tithi, nakṣatra, yoga, karaṇa); chapter 3 treats the gnomon, directions, and the motion of the equinoxes; chapters 4-5 compute lunar and solar eclipses from the nodes; chapter 14 treats the solar divisions of the year. Most pañcāṅga computation into the modern period descends from its methods, and this bundle cites it wherever the siddhāntic formulation carries the point.
