Chandrashtamam begins when the Moon enters the 8th sign from your Moon sign and ends when it leaves. Those two moments depend on where an almanac reckons the Moon to be. Drik reckoning uses a modern ephemeris; vakya reckoning uses traditional tables. The Moon moves about 13 degrees a day, so a small difference in its place becomes hours on the clock. In one printed 1992 column, every entry time matched drik to within a minute and was about two and a half hours from vakya.
☕ Two clocks for one Moon
Chandrashtamam is the Moon in the 8th sign from your Moon sign, counted with your own sign as the 1st (Sanjay Rath, Crux of Vedic Astrology, pp. 89, 240, 245). It begins at the moment the Moon enters that sign and ends at the moment it leaves. So a chandrashtamam time is really a Moon sign-entry time, and two almanacs print different times when they place the Moon differently.
The Moon is fast. It covers about 13 degrees a day, so one degree takes it close to two hours. Drik (thirukanitham) reckoning places the Moon by a modern ephemeris. Vakya reckoning places it by traditional tables handed down in verse. Their Moons are not in the same place, and their sign-entry times can be hours apart (see the page “Vakya vs. Drik”), in the card “What sets a chandrashtamam time” below.
A measured example. A printed Tamil monthly rasi column of 1992 gave fourteen chandrashtamam edges to the minute. Set against the drik (Lahiri) Moon, every one fell within a minute, and the middle value of the differences was 0.2 minutes. Set against a vakya Moon, the middle value was 155 minutes, about two and a half hours. So the times in a printed column are not always from the reckoning a reader expects.
Two smaller causes add to this. Drik almanacs that use different ayanamsas move every sign boundary, and so every entry time (see the page “Ayanamsa Explained”). And a column may print to the half-hour where another prints to the minute.
What Nava follows: drik (Lahiri) positions for the chandrashtamam on its monthly rasi palan pages and in the You tab's month view, whichever panchang you choose. The personal score of each day reads the Moon's sign from the panchang you have chosen, so on a vakya panchang that day's chandrashtamam mark turns at the vakya time.
The moment, not the day
- The start: the moment the Moon enters the 8th sign from your Moon sign.
- The end: the moment the Moon leaves that sign, about two and a quarter days later.
- The Moon's speed: about 13 degrees a day, so one degree of difference moves the time by close to two hours.
- The reckoning: drik and vakya place the Moon differently, so their times can be hours apart.
- The ayanamsa: drik almanacs with different ayanamsas move every entry time.
- The printing: some columns give the half-hour, others the minute.
- The place: none. The moment is the same everywhere; only the clock time changes with the time zone.
- Mix-up: chandrashtamam runs from sunrise to sunrise. It runs from the Moon's entry into the sign to its exit, at any hour.
- Mix-up: a different time means one almanac is wrong. It usually means a different reckoning of the Moon; each is consistent with itself.
- Mix-up: living abroad changes your chandrashtamam. The moment is the same everywhere; only your local clock shows it at a different hour.
Frequently asked questions
Which chandrashtamam time is the right one?
Each is right within its own reckoning. Which almanac a family or a temple keeps to is their choice, not something this page decides. The two differ because they place the Moon differently, not because one forgot a step.
How far apart can drik and vakya chandrashtamam times be?
In the measured 1992 example, the middle difference was about two and a half hours. The gap changes from month to month, because the two reckonings of the Moon drift against each other.
Is chandrashtamam counted by star or by sign?
By sign. It is the Moon in the 8th sign from your Moon sign, so everyone with your Moon sign has the same chandrashtamam, whatever their star.
Deep dive: how the example was measured
What was compared and what the result does and does not show, then what this builds on.
⏱️ Every edge is a sign entry
Each chandrashtamam window in a column starts and ends at a Moon sign change, and the twelve rasis' windows follow one another through the month. That makes every printed edge a test: work out when the Moon entered that sign by each reckoning, for the same place, and compare. The 1992 issue printed to the minute, which is why it gives the sharpest result; earlier issues of the same column printed to the half-hour.
What it shows is which reckoning the column's times came from. It says nothing about which reckoning is right for a ritual, and nothing about the almanac the column appeared beside, which may use its own tables.
🧭 What this builds on
What chandrashtamam is, how long it lasts and how often it comes is on chandrashtamam. How a monthly rasi palan prints it is on how a monthly rasi palan is built.