Lecture Notes: Indian Calendar System

Overview

• Indian calendar can be lunar, solar, or a combination of both.
• A calendar is a cyclical description of time, segmented into years, months, and days.

Vedic Year

• Savana: 12 months of 30 days, totaling 360 days (from Rigveda, 1st Mandala, 164th Sukta, 11th Shloka).
• Different from the modern understanding of a year (365.25 days).
• Vatsara: 12 lunar months, amounting to 354 days.
• Eka Dasharatra Ceremony: Used to sync the lunar cycle to the solar cycle by adding extra days.

Discrepancies and Synchronization

• Authors of the Rigveda were aware of the differences between lunar and solar years.
• Five systems of a year mentioned in Vedic texts:
  1. Sambasara: Solar year, based on the sun passing through 12 zodiacs.
  2. Ida Avatsara: 12 months of 30 days each, totaling 360 days.
  3. Anuvasara: Lunar year, ending on the Amavasya (new moon day).
  4. Vatsara: Year with 12 lunar cycles.
  5. Parivatsara: Based on Jupiter's movement through the zodiac.

Types of Years

• Solar Year: 12 solar months (365 days).
• Savana Year: 12 months of 30 days each (360 days).
• Lunar Year: 12 lunar months (29.5 days each, totaling 354 days).
• Yuga: 5 years cycle to reconcile solar and lunar calendars.
  • 16 solar months and 62 lunar months form a Yuga.
  • Adikamas: An additional month added every 2.5 years.

Month Definitions

• Solar Month (Surya Siddhanta): Time taken by the sun to traverse a Rashi.
• Lunar Month (Chandra Masa): Time interval between two new moons or two full moons.
• Names of lunar months are based on the star positions during full moons.

Pakshas

• Shukla Paksha: Phase from new moon to full moon.
• Krishna Paksha: Phase from full moon back to new moon.

Calculation and Notions

• Vedanga Jyotisha: First text offering algorithms for astronomical calculations like Tithi, Nakshatra, etc.
• Tithi: Angular separation (12 degrees) between Sun and Moon, marking phases of the lunar month.

Conclusion

• These components contribute to the development of the Indian Panchanga (almanac).
• Next topics will delve deeper into the Indian Panchanga.

Note: These notes cover the key points and ideas discussed in the lecture on the Indian calendar system, emphasizing its Vedic origins, different types of years, and methods for synchronization between lunar and solar cycles.