Sandhya means a joining: the twilight where night meets day, and day meets night. Brihat Parashara Hora Shastra gives it two lengths. In one chapter (Vol. 1, p. 112) it is 3 ghatikas, 72 minutes, before the Sun's half-disc rises and the same after it sets. In the chapter on a dasha scheme (Vol. 2, pp. 527–528) it is 5 ghatis on each side of sunrise and of sunset: four hours around each, eight hours a day. Kalaprakasika uses twilight in its rules but gives no length.
☕ Two twilights a day, and two ways to measure them
Every day has two sandhyas: the dawn twilight, before the Sun rises, and the dusk twilight, after it sets. The sky is neither fully dark nor fully lit. Muhurtha books treat this joint as a time of its own, apart from both day and night, in the same way they treat the end of a star or a tithi as a joint.
Brihat Parashara Hora Shastra measures it twice. In Vol. 1 (ch. 9, p. 112) the twilight is 3 ghatikas: 72 minutes before the Sun's half-disc is seen at sunrise, and 72 minutes after it at sunset. In Vol. 2 (ch. 46, pp. 527–528), for a dasha scheme, it is 5 ghatis before and after sunrise, and the same around sunset: a twilight of two hours on each side of the Sun's crossing. The book does not say how the two fit together. Each is stated for its own purpose.
Kalaprakasika names twilight among the times it does not choose for ear-boring (p. 36), for a child's first letters (p. 42) and for upanayanam (p. 52), but gives no length. In its chapter on the Krithika festival it describes twilight as the time the Sun is less than about 18 degrees below the horizon (p. 240). That is a depth, not a clock time: how long it lasts depends on the place and the season. The Brahma muhurtham and pradosham pages explain two other windows near the twilights.
Nava Panchangam does not use this rule in its day score. This page explains it as the books give it.
Two lengths in one book
- 3 ghatikas, 72 minutes
- Dawn: before the Sun's half-disc rises
- Dusk: after it sets
- Sunrise and sunset at 6:00: 4:48–6:00 and 18:00–19:12
- 5 ghatis on each side, 240 minutes per twilight
- Dawn: before and after sunrise
- Dusk: before and after sunset
- Sunrise and sunset at 6:00: 4:00–8:00 and 16:00–20:00
Frequently Asked Questions
Which length is right?
The book gives both and does not rank them. The 3-ghatika twilight is stated for a rule about a birth chart; the 5-ghati twilight on each side is stated for a dasha scheme. Neither chapter is about choosing a muhurtha, so an astrologer decides which, if either, to use for one.
Why does the verse count from the Sun's half-disc?
Sunrise can mean the moment the Sun's top edge appears or the moment its centre does. The verse, with its translator's note, fixes the moment half the disc is seen. Almanacs differ on which moment they print as sunrise, so the same rule can start a few minutes apart in two almanacs.
Is sandhya the same as the time for sandhyavandanam?
The daily prayer is named after the twilight, and is said at it. This page is only about the lengths the astrology books give. The time a family keeps for the prayer follows its own tradition.
Does Kalaprakasika say twilight is a bad time?
It lists twilight among the times it does not choose for ear-boring (p. 36), a child's first letters (p. 42) and upanayanam (p. 52). Those are lists for those functions, not a rule for every day, and the book gives no length for the twilight it means.
How does 18 degrees compare with clock time?
Astronomers also end twilight when the Sun is 18 degrees below the horizon. Near the equator the Sun sinks that far in a little over an hour; far north or south it takes much longer, and in summer it may never get that low. A clock length, like 3 ghatikas, does not change with the place.
From the sources
The two lengths worked out for one day, why the book has two, and what this page leaves out.
🕕 Both lengths on one day
Take a day with sunrise at 6:00 and sunset at 18:00. A ghatika is 24 minutes.
| Rule | Dawn | Dusk |
|---|---|---|
| Brihat Parashara Hora Shastra, Vol. 1, p. 112: 3 ghatikas | 4:48–6:00 | 18:00–19:12 |
| Brihat Parashara Hora Shastra, Vol. 2, pp. 527–528: 5 ghatis each side | 4:00–8:00 | 16:00–20:00 |
The first rule gives 72 minutes on one side of each crossing. The second gives 120 minutes on each side, so its twilight starts earlier and runs on into the day and into the night.
📚 Why one book has two lengths
Brihat Parashara Hora Shastra is a compiled work, and its two volumes have different translators. Each length belongs to the rule it is stated with: the shorter to a rule read from a birth chart (Vol. 1, p. 112), the longer to the division of the day used by a dasha scheme (Vol. 2, pp. 527–528). The book does not choose between them, and this page does not either.
✂️ What this page leaves out
Both chapters use twilight inside rules about a birth: the first in a list of birth combinations, the second in the arithmetic of a dasha scheme. This page keeps the definitions and leaves out what those rules say about the person born, and the dasha arithmetic itself.