Tarabalam and Chandrashtamam: why a good day is not good for everyone

Rahu Kalam and nalla neram are the same for everyone in a town. They are worked out from the sunrise there, so your neighbour's Rahu Kalam is your Rahu Kalam. But before a priest fixes a muhurtham he makes two more checks that are not the same for everyone, because both begin from the person's own birth star. They are tarabalam and chandrabalam.

Tarabalam: counting from your birth star

Your janma nakshatram is the star the Moon stood in at the moment you were born — one of 27, each a little over thirteen degrees of the zodiac. To find the tarabalam for a day, count from your birth star to the star running that day, including both ends, and divide the count by nine. The remainder names one of nine taras:

So fifteen of the 27 stars are favourable for you and twelve are not, and the pattern is different for every birth star. If your star is Ashwini, then Revati — the star just before yours — is Parama Mitra, the best of the nine. For somebody born in Revati the same day is Janma tara, the one to avoid. Nothing about the day changed; only who is asking.

The three cycles

Nine taras cover nine stars, so the cycle runs three times over the 27. Which cycle you land in matters. B. V. Raman, setting out the rule from Muhurta Chintamani, puts it this way: an unfavourable tara in the first cycle of nine counts in full, in the second cycle at about half strength, and in the third it is held to be almost negligible. There are four cases where the texts allow no remedy at all — Janma in the first cycle, Vipat in the second, Pratyari in the third, and Vadha in any cycle — and those days are simply set aside.

Chandrabalam and Chandrashtamam

The second check uses your birth sign, the rasi the Moon was in when you were born. Count from your birth sign to the sign the Moon is in now. The 1st, 3rd, 6th, 7th, 10th and 11th are favourable; the 2nd, 5th and 9th are middling; the 4th and 12th are weak; and the 8th is Chandrashtamam, which is avoided.

The Moon crosses one sign in about two and a quarter days, so Chandrashtamam comes round for roughly that long once every 27 or 28 days, for every person. Families avoid starting anything important during it — signing, travelling, moving into a house. It is worth knowing the exact hours rather than writing off whole days: Chandrashtamam usually begins and ends partway through a day, so the morning may be clear even when the afternoon is not.

Of the two checks, the tradition treats tarabalam as the stronger. Several authorities hold that one may proceed without chandrabalam if tarabalam is sound, but not the other way round.

Why this matters for a family event

For a house warming the date is fixed around the person whose name is on the house; for a wedding, around the couple; for a child's first lesson, around the child. Everyone else in the family is considered, but the main person decides. That is why a date that looks excellent in the printed panchangam can be rejected outright — it may be Vadha tara or Chandrashtamam for the one person it has to suit.

Working this out by hand for four or five relatives across three months is tedious, which is why most families ask an astrologer. The advanced page does the same arithmetic from a birth date and time: it reports both checks for today, or searches ahead for the dates and hours that suit everyone at once. It is a shortlist to take to your priest, not a replacement for him — a full muhurtham also weighs the lagna, the planetary positions and your family's own custom.

Do you need the exact birth time?

It helps a great deal. The Moon changes star about once a day, so without a time the birth star could be the one before or the one after. If the time is genuinely unknown, use what you have and then confirm the star against your horoscope or your family's records — most families know the birth star even when the clock time has been forgotten, because it is used for the yearly star-day.