Panchang in Chahārbāgh, Alborz Province, Iran Sat 21 May 2016

Buddha Purnima follows the tithi at sunrise. Purnima runs from 23:42 on Fri 20 May to 01:44 on Sun 22 May, so it holds sunrise only on Sat 21 May, at 05:57. No text giving Buddha Purnima’s time was found; sunrise is Tithika’s convention.

Buddha Purnima: every date in Chahārbāgh

Purnima follows the tithi at sunrise. Purnima runs from 23:42 on Fri 20 May to 01:44 on Sun 22 May, so it holds sunrise only on Sat 21 May, at 05:57. No text giving Purnima’s time was found; sunrise is Tithika’s convention.

Purnima: every date in Chahārbāgh

The Moon gains on the Sun about 12° a day. Each 12° of lead is one tithi: 168°–180° is the 15th, Shukla Purnima. A day takes the tithi in force at its sunrise, 05:57 here. Chaturdashi ended at 23:42 Fri, before it. Purnima ends at 01:44 Sun, when the lead reaches 180°. The lead passed 0° at the new moon of 6 May, so the Moon is waxing: Shukla paksha.

The night of Fri 20 May ran from sunset 20:09 Fri to sunrise 05:57, 9 h 48 m. Cut into 15 muhurtas of 39 m, its 14th is Brahma Muhurta, the one before the last.

Daylight here, 05:57 to 20:10, splits into 8 choghadiyas of 1 h 46 m. Their names follow a fixed order that starts from the weekday, and each name is counted good, neutral or bad.

The night here, 20:10 to 05:56 Sun, splits into 8 choghadiyas of 1 h 13 m. Their names follow a fixed order that starts from the weekday, and each name is counted good, neutral or bad.

The fixed stars divide the Moon's path into 27 nakshatras of 13°20′, each in 4 padas of 3°20′. Vishakha spans 200°00′–213°20′; the Moon entered its pada 3 at 206°40′. It leaves at 18:09, for Anuradha.

Add the Sun's and the Moon's places among the stars: 36.3° + 207.2° = 243.5°. The sum, cut into 27 parts of 13°20′, gives the yoga: 240°00′–253°20′ is the 19th, Parigha. It ends at 23:59, then Shiva.

A karana is half a tithi: 6° of the Moon's lead, so the first half of Purnima is Vishti and the second Bava. Vishti runs until 12:45, when the lead reaches 174°; Bava until 01:44 Sun.

A Hindu day runs from one sunrise to the next, not midnight to midnight. This one runs 05:57 to 05:56 Sun, so the hours after midnight still belong to Shaniwara.

An amanta month runs from new moon to new moon and takes its name from the rashi the Sun is in at the new moon that begins it: Mesha gives Vaishakha. The Sun enters Vrishabha on 14 May, inside the month. The next new moon, 5 Jun, finds it in Vrishabha and begins Jyeshtha.

A purnimanta month runs from full moon to full moon, so its waning half comes first. It shares its name with the amanta month that its second half falls in: the new moon of 6 May, with the Sun in Mesha, began Vaishakha. This Shukla paksha reads Vaishakha in both counts.

A samvat year begins with Chaitra, the month whose new moon finds the Sun in Meena: 7 Apr 2016, 15:53 Thu. Since then the Sun has moved 42.3° round the stars. Vikram Samvat numbers that year 2073; Shaka Samvat numbers it 1938.