Panchang in Ipameri, Goiás, Brazil Mon 21 Dec 1931

Shiva’s Pradosh puja is done in pradosha, the 3 muhurtas after sunset. Trayodashi began at 19:32 on Mon 21 Dec, before that evening’s pradosha, and ended at 20:45 on Tue 22 Dec, partway into the next. The Nirnayasindhu takes the evening Trayodashi fills: Mon 21 Dec. No text giving Pradosh Vrat’s time was found; pradosha is Tithika’s convention.

Pradosh Vrat: every date in Ipameri

The Moon gains on the Sun about 12° a day. Each 12° of lead is one tithi: 132°–144° is the 12th, Shukla Dwadashi. A day takes the tithi in force at its sunrise, 06:34 here. Ekadashi ended at 17:43 Sun, before it. Dwadashi ends at 19:32, when the lead reaches 144°. The lead passed 0° at the new moon of 9 Dec, so the Moon is waxing: Shukla paksha.

The night of Sun 20 Dec ran from sunset 19:45 Sun to sunrise 06:34, 10 h 49 m. Cut into 15 muhurtas of 43 m, its 14th is Brahma Muhurta, the one before the last.

Daylight here, 06:34 to 19:46, splits into 8 choghadiyas of 1 h 39 m. Their names follow a fixed order that starts from the weekday, and each name is counted good, neutral or bad.

The night here, 19:46 to 06:35 Tue, splits into 8 choghadiyas of 1 h 21 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′. Bharani spans 13°20′–26°40′; the Moon entered its pada 4 at 23°20′. It leaves at 12:42, for Krittika.

Add the Sun's and the Moon's places among the stars: 245.6° + 23.6° = 269.2°. The sum, cut into 27 parts of 13°20′, gives the yoga: 266°40′–280°00′ is the 21st, Siddha. It ends at 02:09 Tue, then Sadhya.

A karana is half a tithi: 6° of the Moon's lead, so the first half of Dwadashi is Bava and the second Balava. Bava runs until 06:42, when the lead reaches 138°; Balava until 19:32.

A Hindu day runs from one sunrise to the next, not midnight to midnight. This one runs 06:34 to 06:35 Tue, so the hours after midnight still belong to Somawara.

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 15 Dec, inside the month. The next new moon, 7 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 9 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: 19 Mar 1931, 04:50 Thu. Since then the Sun has moved 270.7° round the stars. Vikram Samvat numbers that year 1988; Shaka Samvat numbers it 1853.