Panchang in Ipameri, Goiás, Brazil Thu 16 Apr 1981

Shiva’s Pradosh puja is done in pradosha, the 3 muhurtas after sunset. Trayodashi runs from 22:51 on Wed 15 Apr to 00:40 on Fri 17 Apr, so only Thursday’s pradosha (18:02–20:30) 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, 06:22 here. Dwadashi ended at 22:51 Wed, before it. Trayodashi ends at 00:40 Fri, when the lead reaches 156°. The lead passed 0° at the new moon of 4 Apr, so the Moon is waxing: Shukla paksha.

A day takes the tithi in force at its sunrise.

New Delhi · IST

Sunrise here, 05:55, came before Dwadashi ended at 07:21: this day reads Dwadashi.

Ipameri · UTC−3

Sunrise here, 06:22, came after Dwadashi ended at 22:51 Wed: this day reads Trayodashi.

The night of Wed 15 Apr ran from sunset 18:03 Wed to sunrise 06:22, 12 h 19 m. Cut into 15 muhurtas of 49 m, its 14th is Brahma Muhurta, the one before the last.

Daylight here, 06:22 to 18:02, splits into 8 choghadiyas of 1 h 27 m. Their names follow a fixed order that starts from the weekday, and each name is counted good, neutral or bad.

The night here, 18:02 to 06:22 Fri, splits into 8 choghadiyas of 1 h 32 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′. Uttara Phalguni spans 146°40′–160°00′; the Moon entered its pada 2 at 150°. It leaves at 01:45 Fri, for Hasta.

Add the Sun's and the Moon's places among the stars: 2.7° + 150.2° = 152.9°. The sum, cut into 27 parts of 13°20′, gives the yoga: 146°40′–160°00′ is the 12th, Dhruva. It ends at 19:20, then Vyaghata.

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 11:43, when the lead reaches 150°; Taitila until 00:40 Fri.

A Hindu day runs from one sunrise to the next, not midnight to midnight. This one runs 06:22 to 06:22 Fri, so the hours after midnight still belong to Guruwara.

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: Meena gives Chaitra. The Sun enters Mesha on 13 Apr, inside the month. The next new moon, 4 May, finds it in Mesha and begins Vaishakha.

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 4 Apr, with the Sun in Meena, began Chaitra. This Shukla paksha reads Chaitra in both counts.

A samvat year begins with Chaitra, the month whose new moon finds the Sun in Meena: 4 Apr 1981, 17:19 Sat. Since then the Sun has moved 11.3° round the stars. Vikram Samvat numbers that year 2038; Shaka Samvat numbers it 1903.