Panchang in Ipameri, Goiás, Brazil Sat 8 Apr 2017

Shiva’s Pradosh puja is done in pradosha, the 3 muhurtas after sunset. Trayodashi runs from 00:30 on Sat 8 Apr to 01:00 on Sun 9 Apr, so only Saturday’s pradosha (18:08–20:34) 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, 06:20 here. Dwadashi ended at 00:30, before it. Trayodashi ends at 01:00 Sun, when the lead reaches 156°. The lead passed 0° at the new moon of 27 Mar, so the Moon is waxing: Shukla paksha.

A day takes the tithi in force at its sunrise.

New Delhi · IST

Sunrise here, 06:03, came before Dwadashi ended at 09:00: this day reads Dwadashi.

Ipameri · UTC−3

Sunrise here, 06:20, came after Dwadashi ended at 00:30: this day reads Trayodashi.

The night of Fri 7 Apr ran from sunset 18:09 Fri to sunrise 06:20, 12 h 11 m. Cut into 15 muhurtas of 48 m, its 14th is Brahma Muhurta, the one before the last.

Daylight here, 06:20 to 18:08, splits into 8 choghadiyas of 1 h 28 m. Their names follow a fixed order that starts from the weekday, and each name is counted good, neutral or bad.

The night here, 18:08 to 06:20 Sun, splits into 8 choghadiyas of 1 h 31 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′. Purva Phalguni spans 133°20′–146°40′; the Moon entered its pada 3 at 140°. It leaves at 16:02, for Uttara Phalguni.

Add the Sun's and the Moon's places among the stars: 354.6° + 141.5° = 496.1°, one full turn and 136.1°. Past the turn, cut into 27 parts of 13°20′, it gives the yoga: 133°20′–146°40′ is the 11th, Vriddhi. It ends at 00:45 Sun, then Dhruva.

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 12:42, when the lead reaches 150°; Taitila until 01:00 Sun.

A Hindu day runs from one sunrise to the next, not midnight to midnight. This one runs 06:20 to 06:20 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: Meena gives Chaitra. The Sun enters Mesha on 13 Apr, inside the month. The next new moon, 26 Apr, 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 27 Mar, 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: 27 Mar 2017, 23:57 Mon. Since then the Sun has moved 11.1° round the stars. Vikram Samvat numbers that year 2074; Shaka Samvat numbers it 1939.