Panchang in Ipameri, Goiás, Brazil Mon 12 Dec 1921

Shiva’s Pradosh puja is done in pradosha, the 3 muhurtas after sunset. Trayodashi runs from 04:08 on Mon 12 Dec to 03:22 on Tue 13 Dec, so only Monday’s pradosha (18:41–20:51) falls within it. 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: 144°–156° is the 13th, Shukla Trayodashi. A day takes the tithi in force at its sunrise, 05:31 here. Dwadashi ended at 04:08, before it. Trayodashi ends at 03:22 Tue, when the lead reaches 156°. The lead passed 0° at the new moon of 29 Nov, so the Moon is waxing: Shukla paksha.

A day takes the tithi in force at its sunrise.

New Delhi · IST

Sunrise here, 07:04, came before Dwadashi ended at 12:38: this day reads Dwadashi.

Ipameri · UTC−3

Sunrise here, 05:31, came after Dwadashi ended at 04:08: this day reads Trayodashi.

The night of Sun 11 Dec ran from sunset 18:41 Sun to sunrise 05:31, 10 h 50 m. Cut into 15 muhurtas of 43 m, its 14th is Brahma Muhurta, the one before the last.

Daylight here, 05:31 to 18:41, splits into 8 choghadiyas of 1 h 38 m. Their names follow a fixed order that starts from the weekday, and each name is counted good, neutral or bad.

The night here, 18:41 to 05:31 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 3 at 20°. It leaves at 14:24, for Krittika.

Add the Sun's and the Moon's places among the stars: 237° + 21.7° = 258.7°. The sum, cut into 27 parts of 13°20′, gives the yoga: 253°20′–266°40′ is the 20th, Shiva. It ends at 18:43, then Siddha.

A karana is half a tithi: 6° of the Moon's lead, so the first half of Trayodashi is Kaulava and the second Taitila. Kaulava runs until 15:50, when the lead reaches 150°; Taitila until 03:22 Tue.

A Hindu day runs from one sunrise to the next, not midnight to midnight. This one runs 05:31 to 05:31 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, 29 Dec, 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 29 Nov, 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: 8 Apr 1921, 06:04 Fri. Since then the Sun has moved 241.8° round the stars. Vikram Samvat numbers that year 1978; Shaka Samvat numbers it 1843.