Rahu Kalam, Yamaganda and Gulika: where the tables come from

Definition

Rahu Kalam, Yamaganda and Gulika are three time windows that a panchang prints for every day. Each is one eighth of the daylight, from sunrise to sunset; which eighth depends on the weekday.

Formula

part = (sunset − sunrise) ÷ 8. The window for part n runs from sunrise + (n − 1) × part to sunrise + n × part. The weekday tables, Sunday to Saturday: Rahu Kalam 8, 2, 7, 5, 6, 4, 3; Yamaganda 5, 4, 3, 2, 1, 7, 6; Gulika 7, 6, 5, 4, 3, 2, 1. Every modern panchang checked uses these tables, except one site that moves Yamaganda and Gulika one part earlier.

Worked example

A Monday with sunrise at 06:00 and sunset at 18:00: 12 hours of daylight, so each part is 1 hour 30 minutes. Rahu Kalam is part 2, 07:30 to 09:00. Yamaganda is part 4, 10:30 to 12:00. Gulika is part 6, 13:30 to 15:00.

The eighths of the day in BPHS

Brihat Parashara Hora Shastra, as printed (chapter 3, verses 66 to 69 in R. Santhanam's translation), divides the day into eight equal parts and gives the first seven to the planets in weekday order (Sun, Moon, Mars, Mercury, Jupiter, Venus, Saturn), starting with the lord of the weekday. The eighth part has no lord. Saturn's part is named Gulika, and Jupiter's Yamaghantaka.

That rule reproduces both modern tables exactly. On Sunday the count runs Sun 1, Moon 2, Mars 3, Mercury 4, Jupiter 5, Venus 6, Saturn 7: Yamaganda is part 5 and Gulika part 7. On Monday it starts from the Moon, so Jupiter's part is 4 and Saturn's 6. The variant that moves both one part earlier therefore disagrees with BPHS.

Rahu Kalam has no such rule

Rahu has no part in that scheme: seven planets take seven parts and the eighth is lordless. Rahu Kalam's parts match no single planet's. On Sunday its part 8 is the lordless one; on Monday its part 2 is Mars's; on Tuesday its part 7 is the Moon's.

No rule for Rahu Kalam was found in BPHS, Phaladeepika, Jataka Parijata, Muhurta Chintamani or Muhurta Martanda. The earliest mention found is a passing one in Uttara Kalamrita (Kanda 2, verse 29). Its translator, P. S. Sastri, dates that text after the 16th century and notes that Rahu Kala is observed especially in Tamil Nadu, Karnataka and Kerala and is not mentioned in the standard texts. The weekday table appears in 20th-century books by N. P. Subramania Iyer and B. V. Raman, without a source.

Names

BPHS spells Yamaganda yamaghantaka, from yama and ghanta, a bell (Monier-Williams); the common spelling with ganda is often read as Yama's danger. Jataka Parijata (2.5) calls Gulika the son of Saturn; BPHS calls it only Saturn's part. Gulika is also called Mandi.

How Jyotishya uses them

The day clock shows all three windows for where you live now, or else your birthplace. Sunrise and sunset come from Astronomy Engine, using the upper edge of the Sun and standard refraction, as Drik Panchang does. The windows are labelled reference, with the tradition stated, and are not in any score.