Paksha: the bright and dark halves
A Hindu lunar month has two pakshas, Shukla (the waxing, bright fortnight) and Krishna (the waning, dark fortnight), each with 15 tithis.
Two halves of the month
Paksha = fortnight, literally "wing". A lunar month has two wings: the half in which the Moon grows brighter and the half in which it fades. Each paksha contains 15 tithis and lasts a little under 15 days, though the exact length varies because tithis vary.
| Shukla paksha | Krishna paksha | |
|---|---|---|
| Meaning | Bright half | Dark half |
| Moon | Waxing, growing | Waning, shrinking |
| Begins after | Amavasya (new Moon) | Purnima (full Moon) |
| Ends with | Purnima (full Moon) | Amavasya (new Moon) |
Names for the halves differ by language. In Gujarati calendars the bright half is written Sud and the dark half Vad. Other regional calendars use similar short forms.
Shukla paksha
The word shukla means bright or white. It starts the day after the new Moon and the crescent grows each night until Purnima. Its tithis are numbered Shukla Pratipada, Shukla Dwitiya and so on, up to Shukla Chaturdashi and Purnima.
Many major festivals fall in the Shukla paksha, for example Navratri, Ram Navami and Ganesh Chaturthi. Traditionally the growing light is associated with beginnings, growth and celebration.
Krishna paksha
The word krishna means dark. It begins after the full Moon, and the Moon shrinks until Amavasya. Tithis are numbered in the same way: Krishna Pratipada to Krishna Chaturdashi, then Amavasya.
Some festivals and observances are in the dark half. Diwali falls on Amavasya, and Maha Shivaratri on Chaturdashi. The dark half is also the time of ancestor rites such as Pitru Paksha, the fortnight devoted to ancestors.
Do not treat the dark half as unlucky. Krishna paksha has many important observances, and nothing in it is unlucky in itself.
Naming a date
A full Hindu date uses three parts: the month, the paksha and the tithi. "Chaitra Shukla Navami" means the ninth tithi of the bright half of the month of Chaitra. This is how festival dates are described in these pages, because it is the same each year while the Gregorian date changes.
The paksha and the month name
This is where regional difference appears. The Shukla paksha has the same month name in both main systems. The Krishna paksha has different names.
In the Purnimanta system the month ends on Purnima, so the Krishna paksha after the full Moon of Chaitra already belongs to the next month, Vaishakha. In the Amanta system the month ends on Amavasya, so that same fortnight is still Chaitra. See the page on Amanta and Purnimanta for details.
So when a source says "Krishna Chaturdashi", ask which month system it uses. The site shows both names to avoid confusion.
Paksha in daily life
Many families look at the paksha for fasting and puja. Ekadashi occurs in both halves, so there are two each month. Chaturthi has a Shukla form (Vinayaka) and a Krishna form (Sankashti), both linked to Ganesha. Knowing the paksha tells you which one is meant.