Panchang Explained: Five Limbs and Rahu Kaal

A panchang is the Hindu calendar for a single day, and the word means five limbs: tithi, nakshatra, yoga, karana and vara. A Gregorian calendar tells you the date. A panchang tells you the state of the sky on that date, which is what traditional practice consults before fixing a wedding, opening a shop or starting a journey.

Every value in it is astronomical. Tithi comes from the angle between the Sun and Moon. Nakshatra comes from where the Moon sits against the fixed stars. Rahu Kaal comes from your local sunrise, which is why the panchang for Chennai is not the panchang for Delhi.

The five limbs, and what each one actually measures

Tithi is the lunar day. It is defined as 12 degrees of angular separation between the Sun and the Moon, so a lunar month contains 30 of them: fifteen in the waxing Shukla Paksha and fifteen in the waning Krishna Paksha. Because the Moon travels on an ellipse and changes speed, a tithi is not a fixed length. It runs anywhere from about 19 to 26 hours. This is the single fact that confuses most people reading a panchang for the first time: the tithi rarely changes at midnight, and a calendar date can carry two of them.

Nakshatra is the lunar mansion. The ecliptic is divided into 27 segments of 13 degrees 20 minutes each, and the Moon passes through roughly one per day. Same caveat as tithi, for the same reason: the changeover lands wherever it lands, often mid-afternoon.

Yoga is calculated by adding the longitudes of the Sun and Moon and dividing the result into 27 parts. It has nothing to do with the physical practice that shares the name. Some yogas carry good reputations and some carry warnings, but in practice it is the least consulted of the five.

Karana is half a tithi, which means two of them fall inside every lunar day. There are eleven types. Four appear once per lunar month and seven repeat eight times each.

Vara is the weekday, and each is ruled by a planet: Sunday by the Sun, Monday by the Moon, Tuesday by Mars, Wednesday by Mercury, Thursday by Jupiter, Friday by Venus, Saturday by Saturn. The order looks arbitrary until you notice it comes from the sequence of planetary hours, which is also where the seven-day week itself comes from.

Rahu Kaal is not a fixed time of day

This is the part most often got wrong. Rahu Kaal is not "half past four" or any other clock time. It is one eighth of the daylight period, and which eighth depends on the weekday.

Take the time from sunrise to sunset, divide it into eight equal parts, and count:

• Sunday, the eighth part
• Monday, the second part
• Tuesday, the seventh part
• Wednesday, the fifth part
• Thursday, the sixth part
• Friday, the fourth part
• Saturday, the third part

Two consequences follow. First, Rahu Kaal moves through the year, because daylight in June is longer than daylight in December, so each eighth is longer too. In north India a summer Rahu Kaal can run close to 100 minutes while a winter one runs closer to 75. Second, it moves by city. Sunrise in Kolkata is roughly forty minutes ahead of sunrise in Mumbai, and Rahu Kaal shifts with it.

What tradition asks of you during that window is narrow. Avoid beginning something new: a venture, an agreement, a journey. Work already under way is generally treated as unaffected, and where the timing cannot be helped, classical practice is a good deal more relaxed about it than most websites are. Rahu Kaal is guidance about when to start, not a claim about how things will turn out.

Choghadiya, for when you need something finer

Rahu Kaal marks one window to avoid. Choghadiya divides the whole day into eight parts and the night into eight more, and gives each a name and a character:

• Amrit, the most favourable
• Shubh, good, traditionally for religious work and meetings
• Labh, good, traditionally for business and money matters
• Char, neutral, and held to suit travel
• Rog, Kaal and Udveg, the three to work around

The sequence rotates by weekday, so the same clock hour carries a different Choghadiya on Tuesday than on Friday. Shopkeepers across north and west India still open on a Labh period out of habit rather than calculation.

Why two panchangs disagree about the same day

If you check two sites and get different answers, both may be right. There are two ordinary reasons.

The first is location, which we have covered. Anything derived from sunrise moves with your longitude and latitude.

The second is ayanamsa, the correction between the tropical zodiac used in Western astrology and the sidereal zodiac used in Jyotish. The two coincided around the fifth century CE and have drifted apart since, at roughly one degree every 72 years. They now sit about 24 degrees apart. Different schools use slightly different values for that correction. Lahiri, the Indian government standard, is the most widely used in India. A site using a different ayanamsa will show nakshatra and tithi changeovers a little earlier or later than one using Lahiri. The gap is usually minutes, occasionally enough to move a changeover across midnight and change which nakshatra a date is labelled with.

Neither reason makes anybody wrong. It helps to know which ayanamsa your source uses and stay with one.

What a panchang will not do

It describes the day everybody is sharing. It says nothing about you specifically.

That distinction matters more than it sounds. Today's nakshatra is where the Moon is right now, the same for every reader of this page. Your birth nakshatra is where the Moon stood at the moment you were born, and it does not change for the rest of your life. Panchang is the weather report; your birth chart is the terrain. A transit only means something in relation to the chart it is passing over, which is why "today is Rohini" tells you far less than it appears to.

The practical use is timing. When you already know what you want to do, the panchang helps you pick an hour for it. That is the whole job, and it is a useful one.

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You can check today's panchang for your city free, with the tithi and nakshatra end times and the Choghadiya period running right now. If you want to know your own birth nakshatra rather than today's, the free kundli will calculate it from your date, time and place of birth.