Māsa · lunar month
Meet the twelve lunar months
Māsa means month. In the amānta system used by this calendar, a lunar month runs from one New Moon boundary to the next. The month's Sanskrit name comes from the Sun's sidereal-zodiac passage during that lunation.
A different idea of “month”
Lunar and Gregorian months use different boundaries.
Begins at local midnight on day 1 and contains 28, 29, 30, or 31 whole civil dates.
Its boundaries follow a fixed civil-calendar grid.
Begins and ends at successive New Moon boundaries and lasts about 29½ days.
Its boundary is an astronomical instant, which can occur at any local clock time.
Because the systems use different boundaries, one amānta month usually occupies parts of two Gregorian months. Its Gregorian dates move from year to year, and the local date containing a boundary can differ by time zone. Āṣāḍha therefore overlaps portions of Gregorian months rather than corresponding to “July.”
What the calculation does
Find two New Moons, then check the sidereal solar ingress between them.
A month system in which the lunar month ends at Amāvasyā, the New Moon boundary.
The Sun's entry into a new sidereal zodiac sign. The sign entered supplies the ordinary amānta month name shown here.
An intercalary, or additional, lunar month that occurs when no sidereal solar ingress falls between two New Moons.
A rare “omitted” month situation associated with two solar ingresses in one lunation. When this occurs, Open Pañcāṅga withholds the month name for review.
A named way of locating the starting point of the star-referenced zodiac. Its angular distance from the seasonal starting point supplies the value used in calculation. For the lunar-month names on this page, Open Pañcāṅga uses an approximate Lahiri (Citrāpakṣa) convention.
An ordinary lunation containing one sidereal solar ingress. That ingress determines the name shown below.
The annual sequence
The twelve regular amānta month names
Under the amānta method explained here, the sidereal sign entered by the Sun between successive New Moons supplies the corresponding month name. The English sign names are included only as vocabulary aids.
| Order | Māsa · lunar month | Sidereal solar entry during the lunation |
|---|---|---|
| 1 | Caitra | Meṣa · Aries |
| 2 | Vaiśākha | Vṛṣabha · Taurus |
| 3 | Jyeṣṭha | Mithuna · Gemini |
| 4 | Āṣāḍha | Karka · Cancer |
| 5 | Śrāvaṇa | Siṃha · Leo |
| 6 | Bhādrapada | Kanyā · Virgo |
| 7 | Āśvina | Tulā · Libra |
| 8 | Kārttika | Vṛścika · Scorpio |
| 9 | Mārgaśīrṣa | Dhanu · Sagittarius |
| 10 | Pauṣa | Makara · Capricorn |
| 11 | Māgha | Kumbha · Aquarius |
| 12 | Phālguna | Mīna · Pisces |
This table follows the amānta system explained on this page. A pūrṇimānta system places the month boundary at the Full Moon instead, so the same date can receive a different month name under that system.
When the answer is uncertain
Near a sign boundary, the application withholds the month name.
Open Pañcāṅga uses live NASA/JPL Horizons longitudes and a documented Lahiri (Citrāpakṣa) approximation: 23°51′11″ at J2000 plus 50.29 arcseconds per tropical year. New Moon boundaries are estimated from six-hour samples. If a New Moon falls within 0.5 degrees of a sidereal-sign boundary, the result explicitly withholds the uncertain month name. Any annual observance depending on that month is also withheld rather than guessed.