Paksha

The Hindu lunar month is divided into two pakshas of roughly 15 days each. Shukla Paksha begins after Amavasya (new moon) and ends at Purnima (full moon), with the Moon waxing brighter each night. Krishna Paksha begins after Purnima and ends at Amavasya, with the Moon waning toward darkness. This division is fundamental to the entire Hindu calendar system — dates are expressed as a tithi within a paksha (e.g., "Shukla Ekadashi" or "Krishna Ashtami").

The two pakshas carry distinct spiritual and practical significance. Shukla Paksha is generally considered more auspicious for new beginnings, marriages, business launches, and constructive activities — the waxing Moon symbolizes growth and accumulation. Krishna Paksha is traditionally preferred for introspective practices, ancestor worship (shraddha and tarpan), tantra sadhana, and activities requiring dissolution or completion. However, many important festivals fall in Krishna Paksha — Maha Shivaratri (Krishna Chaturdashi) and Krishna Janmashtami (Krishna Ashtami) being prominent examples.

Tithimala determines the current paksha by computing the Sun-Moon angular difference. When the Moon is 0° to 180° ahead of the Sun (in longitude), it is Shukla Paksha; from 180° to 360° it is Krishna Paksha. Swiss Ephemeris provides the precise positions needed for this determination, accounting for the irregularities in the Moon's orbit that cause pakshas to vary slightly in duration from month to month.

Understanding paksha is essential for interpreting any panchang correctly, since the same tithi number (e.g., Chaturthi) has entirely different ritual significance depending on whether it falls in Shukla or Krishna Paksha.