Tithi Explained: The Thirty Lunar Days

In one paragraph

A tithi is the lunar day of the Hindu calendar, defined by geometry rather than by the clock: one tithi is the time the Moon takes to increase its angular distance from the Sun by exactly 12 degrees. Thirty tithis carry the Moon through the full 360 degrees, completing a lunar month. Because the Moon travels at a variable speed along its elliptical orbit, that 12-degree step takes a variable time — from roughly 19 to roughly 26 hours, averaging about 23 hours and 37 minutes. That single fact explains almost everything confusing about Hindu dates. A tithi shorter than the gap between two sunrises can slip through without touching one and is skipped (kshaya); a longer one spans two sunrises and is repeated (adhika). Since the tithi at sunrise names the day, festivals fixed by tithi appear to jump, fall back or occupy two days depending on where you stand. Tithi is the first of the five limbs of the Panchang, computed for your exact place on the Panchang page.

What a tithi actually is

Forget the calendar and watch two objects. The Sun moves along the ecliptic at about one degree per day; the Moon covers the same path at 12 to 15 degrees per day. What matters is the gap between them — the elongation, the Moon's longitude minus the Sun's, measured forwards to 360 degrees.

At new moon that gap is zero; at full moon it is 180 degrees. Slice the circle into thirty arcs of 12 degrees and each arc is one tithi. A tithi is not a duration someone chose; it is an angle that is crossed, and its length is whatever the sky gives it.

Two consequences follow. First, a tithi begins and ends at a precise instant, not at midnight or sunrise. Shukla Panchami might begin at 3:12 pm and end at 11:47 the next morning; every honest panchang prints both timestamps.

Second, tithi is independent of the ayanamsha. Because it is a difference between two longitudes, the constant converting tropical positions into sidereal ones cancels out. That is unusual in Jyotisha: your rashi and nakshatra shift if the ayanamsha shifts, as our note on what ayanamsha is explains — your tithi does not.

Why a tithi is not twenty four hours long

Most pages skate over this. The Moon's orbit is an ellipse, not a circle. Near perigee it moves fastest, up to about 15.4 degrees a day; near apogee it slows to about 11.8 degrees a day. The Sun's apparent motion also varies, between about 0.95 and 1.02 degrees a day, the Earth's orbit being elliptical too. The tithi is governed by the difference:

Condition	Relative speed per day	Tithi length
Near perigee	about 14.4 degrees	about 20 hours
Average	about 12.2 degrees	about 23 hours 37 minutes
Near apogee	about 10.7 degrees	about 26 to 27 hours

So a tithi is never reliably a day long. It is usually a little shorter than a solar day, sometimes much shorter, occasionally longer.

Thirty tithis fit into a lunar month of about 29.53 days. Thirty units squeezed into twenty-nine and a half days leaves the system structurally over-supplied: roughly half a tithi a month has nowhere to go.

A year holds about 371 tithis but only about 365 days, so about six more tithis must be dropped than added. That is not an error in anyone's calculation; it is what a 12-degree ruler does to a Moon that will not keep pace.

Skipped and repeated tithis, kshaya and adhika

Attach the tithi to the calendar and two famous anomalies appear.

Kshaya tithi, the skipped lunar day. If a tithi begins after sunrise and ends before the next sunrise, no sunrise falls inside it, so it never gets a day of its own. It is kshaya — decayed, lost. The calendar jumps: Saptami, then Navami, with Ashtami missing entirely. Ashtami did occur; it simply occurred between two sunrises. Kshaya tithis cluster near perigee, when tithis are shortest.

Adhika or vriddhi tithi, the repeated lunar day. If a tithi lasts longer than the gap between two sunrises, it can be running at two consecutive sunrises, and both days carry the same name: Dashami on Tuesday, Dashami again on Wednesday. It is adhika (extra) or vriddhi (grown). These cluster near apogee.

Three clarifications, because this is where readers get lost:

• An adhika tithi is not an adhika masa. The adhika masa is the intercalary thirteenth month inserted every 32 to 33 months to hold the lunar year to the solar. Same adjective, different mechanism.
• A skipped tithi does not skip the observance. If Ekadashi is kshaya, the tradition still resolves a day for the fast by its own rules. Nothing is cancelled.
• Neither is a defect. Skips and repeats are the correct behaviour of an angle-based calendar. One that never skipped would have quietly stopped tracking the Moon.

This is the honest reason your family panchang and a friend's app can print Ganesh Chaturthi or Janmashtami one day apart: when a tithi straddles a sunrise or vanishes between two, different authorities apply different tie-breaking rules, each faithful to its own lineage.

The tithi at sunrise governs the day

In most Indian reckonings the civil day begins at local sunrise, not midnight, and inherits the tithi running at that sunrise. That is why a tithi is treated as owning a whole day though its true boundaries fall at odd hours.

The consequence is geographic. Sunrise in Guwahati is well over an hour earlier than in Ahmedabad. If a tithi changes inside that window, the two cities genuinely have different tithis on the same calendar date, and neither is wrong. It is why an almanac keyed to one city is only approximate for another, and why a computed Panchang asks for your place first.

The same logic governs the other limbs — vara, nakshatra, yoga and karana — and the day divisions in our guide to nakshatra and Choghadiya. Note that a karana is exactly half a tithi, a 6-degree step, so there are two karanas in every tithi.

All thirty tithis

The lunar month splits into two pakshas of fifteen tithis. Shukla Paksha is the bright, waxing fortnight from new moon to full moon; Krishna Paksha is the dark, waning fortnight back to new moon. The first fourteen names are identical in both; only the fifteenth differs. The bright fortnight closes with Purnima, the full moon, the dark with Amavasya, the new moon.

No.	Tithi	Group	Elongation in Shukla Paksha (degrees)	Elongation in Krishna Paksha (degrees)
1	Pratipada	Nanda	0 to 12	180 to 192
2	Dwitiya	Bhadra	12 to 24	192 to 204
3	Tritiya	Jaya	24 to 36	204 to 216
4	Chaturthi	Rikta	36 to 48	216 to 228
5	Panchami	Purna	48 to 60	228 to 240
6	Shashthi	Nanda	60 to 72	240 to 252
7	Saptami	Bhadra	72 to 84	252 to 264
8	Ashtami	Jaya	84 to 96	264 to 276
9	Navami	Rikta	96 to 108	276 to 288
10	Dashami	Purna	108 to 120	288 to 300
11	Ekadashi	Nanda	120 to 132	300 to 312
12	Dwadashi	Bhadra	132 to 144	312 to 324
13	Trayodashi	Jaya	144 to 156	324 to 336
14	Chaturdashi	Rikta	156 to 168	336 to 348
15	Purnima or Amavasya	Purna	168 to 180	348 to 360

Read the elongation column and the Moon's appearance follows. On Shukla Ashtami it stands 90 degrees from the Sun, showing a clean half disc in the evening sky; on Krishna Ashtami it is 270 degrees along, showing the opposite half near midnight. None of this is symbolic; it is simply what the sky is doing, as our profile of Chandra, the Moon in Vedic astrology explains.

The five groups, Nanda to Purna

Divide the tithi number by five. The remainder sorts all thirty into five families, each with a character used in muhurta, the choice of favourable times.

Group	Tithis	Sense of the name	Traditionally suited to
Nanda	1, 6, 11	Joyful	Celebration, art, ornament, pleasant beginnings
Bhadra	2, 7, 12	Gentle	Steady work, foundations, travel, routine business
Jaya	3, 8, 13	Victorious	Contests, disputes, tasks needing resolve
Rikta	4, 9, 14	Empty	Removal, demolition, endings; avoided for beginnings
Purna	5, 10, 15	Full	Completion, ceremonies, long journeys, lasting work

Many muhurta texts also assign graha lords — Nanda to Shukra, Bhadra to Budha, Jaya to Mangal, Rikta to Shani, Purna to Guru — though this varies regionally, so treat it as one convention rather than settled doctrine.

The practical takeaway is the Rikta row. Rikta means empty, and Chaturthi, Navami and Chaturdashi are traditionally avoided for launching anything — a business, a marriage, a construction, a journey of consequence. With the Choghadiya time bands, this is the everyday muhurta layer most families actually practise.

Notice the tension rather than papering over it: Ganesh Chaturthi, Ram Navami and Anant Chaturdashi are all Rikta tithis, and all are major festivals. The caution applies to worldly enterprises, not to worship or fasting. A tithi unsuited to signing a lease can suit a vrat perfectly.

Observances fixed by tithi and not by date

Much of the ritual year is anchored to tithi, not to a fixed date, which is why these must be looked up afresh each month.

• Ekadashi — the eleventh tithi of both fortnights, so roughly twenty-four a year, and two more in a year carrying an intercalary month. Kept with a grain-free fast and a prescribed breaking time, the parana.
• Pradosh — Trayodashi, observed to Shiva in the twilight window around sunset rather than at sunrise. Twice a lunar month.
• Sankashti Chaturthi — the Chaturthi of Krishna Paksha, dedicated to Ganesha, the fast broken at moonrise rather than at a solar marker. On a Tuesday it is called Angarki.
• Purnima — the full moon, carrying Guru Purnima, Buddha Purnima, Sharad Purnima and Kartik Purnima.
• Amavasya — the new moon, associated with rites for the ancestors, including Mahalaya Amavasya and the Kartik Amavasya of Diwali.

Each depends on where a moving tithi boundary falls relative to sunrise, moonrise or twilight at your location, so a single national date is always an approximation. Kaalveda's festival calendar and today's panchang resolve them against a place.

Honest limits

The astronomy of tithi is not in dispute: two competent ephemerides agree on when a tithi begins to within seconds. What follows is where honesty is owed.

Panchangs still disagree, for real reasons. Even though tithi is ayanamsha-independent, almanacs differ on drik (true) versus older mean computation, on how sunrise is defined (upper limb or disc centre, with or without refraction), and above all on the applicability rules deciding which day carries a festival when a tithi is skipped or repeated. Two panchangs can compute an identical tithi and still print Diwali on different days.

Month naming differs regionally. Under amanta reckoning a month ends at Amavasya; under purnimanta it ends at Purnima. The same Krishna Paksha tithi therefore sits in Shravana in the north and Bhadrapada in the west and south. Same day, different month label.

The qualities are convention, not measurement. The 12-degree definition is astronomy. That a Rikta tithi is unfavourable for beginnings is traditional muhurta doctrine — long transmitted, not demonstrated by controlled evidence. Kaalveda reports both and labels which is which.

Tithi is not a substitute for judgement. No lunar day supplies medical, legal or financial advice. If a decision carries real consequences, take professional counsel first and let the muhurta pick the hour, not the choice.

Where to start

• What is Panchang and the Panchang calendar — the hub article; tithi is the first of its five limbs
• Panchang for your city — tithi start and end times for your exact place
• Nakshatra and Choghadiya explained — the limbs beside tithi
• Chandra, the Moon in Vedic astrology — the variable speed behind it all
• What is ayanamsha — and why tithi is unaffected by it
• Festival calendar — Ekadashi, Pradosh, Purnima and Amavasya resolved to dates
• Today's panchang and Choghadiya — the everyday muhurta layer
• Free kundli — your birth tithi with your lagna, rashi and nakshatra