The Indian horoscope: the lunar calendar behind it

Anyone who opens an Indian reading runs straight into words that do not occur in the Western horoscope: tithi, panchanga, nakshatra. There is no secret knowledge behind them, only a calendar. It is built differently from the one you fix your appointments by, and anyone who understands it also understands why an Indian interpretation speaks so often of the Moon and so rarely of the Sun.

Months named after lunar mansions

In this calendar a month runs from one new moon to the next; in northern India it is usual to let it end at the full moon instead — the same weeks, divided up differently. Its name comes from the sky: it is called after the lunar mansion in which that month's full moon stands. The month of Kartika therefore carries the name of the Krittika, the small group of stars known in the West as the Pleiades, or the Seven Sisters.

Because twelve turns of the Moon come out shorter than a solar year, a thirteenth month is slipped in from time to time; otherwise the months would drift out of their season little by little. An Indian festival therefore has no fixed date in the Western calendar, but it does have a fixed season. Anyone who simply calls Kartika November will be wrong again the following year.

The tithi: a day with no fixed length

This is the unit most people get stuck on, and it is the most revealing of them. A tithi does not measure the turning of the Earth but the distance between Moon and Sun. Every time that distance has grown by twelve degrees, a tithi is over. From new moon to full moon there are fifteen of them, and fifteen more on the way back: thirty lunar days in a month.

Because the Moon and the Sun do not advance at an even speed as seen from the Earth, a tithi runs now shorter, now longer — just under twenty-four hours on average, and noticeably under or over that in a given case. Nor does it begin at midnight: it can begin at any hour at all. Hence the usual convention that the tithi running at sunrise gives the calendar day its name.

Five limbs make up a day

Panchanga means, literally, five limbs, and that is how many details belong to a fully determined day: the tithi, the day of the week, the lunar mansion the Moon is standing in, and two further quantities drawn from the positions of Sun and Moon, called yoga and karana. An Indian calendar is therefore not a column of figures but, for each day, a small profile.

One of those limbs will look familiar to you. The seven days of the week carry the same seven rulers as in the West, and in the same order: Sun, Moon, Mars, Mercury, Jupiter, Venus, Saturn. Sunday, Monday and Saturday still say so outright; in Tuesday, Wednesday, Thursday and Friday the Roman gods have been replaced by Germanic ones. German has let two of them fall out of line — its Wednesday merely counts the middle of the week, its Saturday goes back to the Sabbath. In French, Mars, Mercury, Jupiter and Venus sit unchanged in the names to this day. What the celestial bodies mean in an interpretation is set out under the planets.

Why interpretation begins with the Moon

If the calendar is built from the Moon, it stands to reason that the birth chart starts there too. What is asked for is the lunar mansion the Moon stood in at birth, and the tithi of that day. In many families the birthday is still kept by this lunar day and not by the date on the identity papers; the two rarely coincide.

The same arithmetic fixes the festivals: Diwali falls on a new moon, Holi on a full moon. And it has a say in the choice of moments — for a wedding or a move, a day is sought whose five limbs suit the undertaking. This calendar is the piece of Jyotisha that really is used in daily life.

What you can do with it

If a tithi appears in a reading, what you have in front of you is a checkable detail and not a description of a mood: whether the Moon was waxing or waning on your birthday you can look up in any lunar calendar, and how far it stood from the Sun at the time follows from that. And the day your lunar birthday falls on this year is settled by no astrologer but by a panchanga. How a third tradition divides up its time is shown, for comparison, by Chinese astrology.