Panchang in Myshkin, Yaroslavl Oblast, Russia Sat 22 Dec 2018

Purnima follows the tithi at sunrise. Purnima runs from 23:39 on Fri 21 Dec to 20:48 on Sat 22 Dec, so it holds sunrise only on Sat 22 Dec, at 09:09. No text giving Purnima’s time was found; sunrise is Tithika’s convention.

Purnima: every date in Myshkin

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, 09:09 here. Chaturdashi ended at 23:39 Fri, before it. Purnima ends at 20:48, when the lead reaches 180°. The lead passed 0° at the new moon of 7 Dec, so the Moon is waxing: Shukla paksha.

The night of Fri 21 Dec ran from sunset 15:39 Fri to sunrise 09:09, 17 h 30 m. Cut into 15 muhurtas of 1 h 10 m, its 14th is Brahma Muhurta, the one before the last.

Daylight here, 09:09 to 15:39, splits into 8 choghadiyas of 48 m. Their names follow a fixed order that starts from the weekday, and each name is counted good, neutral or bad.

The night here, 15:39 to 09:09 Sun, splits into 8 choghadiyas of 2 h 11 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′. Mrigashira spans 53°20′–66°40′; the Moon entered its pada 2 at 56°40′. It leaves at 20:44, for Ardra.

Add the Sun's and the Moon's places among the stars: 246.2° + 59.6° = 305.8°. The sum, cut into 27 parts of 13°20′, gives the yoga: 293°20′–306°40′ is the 23rd, Shubha. It ends at 10:30, then Shukla.

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 10:16, when the lead reaches 174°; Bava until 20:48.

A Hindu day runs from one sunrise to the next, not midnight to midnight. This one runs 09:09 to 09:09 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: Vrishchika gives Margashirsha. The Sun enters Dhanu on 16 Dec, inside the month. The next new moon, 6 Jan, finds it in Dhanu and begins Pausha.

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 7 Dec, with the Sun in Vrishchika, began Margashirsha. This Shukla paksha reads Margashirsha in both counts.

A samvat year begins with Chaitra, the month whose new moon finds the Sun in Meena: 17 Mar 2018, 16:11 Sat. Since then the Sun has moved 273.4° round the stars. Vikram Samvat numbers that year 2075; Shaka Samvat numbers it 1940.