Panchang in Codcod, Western Visayas, Philippines Sun 31 Dec 2017

Shiva’s Pradosh puja is done in pradosha, the 3 muhurtas after sunset. Trayodashi runs from 21:25 on Sat 30 Dec to 17:58 on Sun 31 Dec, so it touches only Sunday’s pradosha (17:35–20:05). No text giving Pradosh Vrat’s time was found; pradosha is Tithika’s convention.

Pradosh Vrat: every date in Codcod

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, 06:04 here. Dwadashi ended at 21:25 Sat, before it. Trayodashi ends at 17:58, when the lead reaches 156°. The lead passed 0° at the new moon of 18 Dec, so the Moon is waxing: Shukla paksha.

The night of Sat 30 Dec ran from sunset 17:35 Sat to sunrise 06:04, 12 h 29 m. Cut into 15 muhurtas of 49 m, its 14th is Brahma Muhurta, the one before the last.

Daylight here, 06:04 to 17:35, splits into 8 choghadiyas of 1 h 26 m. Their names follow a fixed order that starts from the weekday, and each name is counted good, neutral or bad.

The night here, 17:35 to 06:04 Mon, splits into 8 choghadiyas of 1 h 33 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′. Rohini spans 40°00′–53°20′; the Moon entered its pada 2 at 43°20′. It leaves at 20:23, for Mrigashira.

Add the Sun's and the Moon's places among the stars: 255.3° + 44.3° = 299.6°. The sum, cut into 27 parts of 13°20′, gives the yoga: 293°20′–306°40′ is the 23rd, Shubha. It ends at 16:34, then Shukla.

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 07:44, when the lead reaches 150°; Taitila until 17:58.

A Hindu day runs from one sunrise to the next, not midnight to midnight. This one runs 06:04 to 06:04 Mon, so the hours after midnight still belong to Raviwara.

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: Dhanu gives Pausha. The Sun enters Makara on 14 Jan, inside the month. The next new moon, 17 Jan, finds it in Makara and begins Magha.

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 18 Dec, with the Sun in Dhanu, began Pausha. This Shukla paksha reads Pausha in both counts.

A samvat year begins with Chaitra, the month whose new moon finds the Sun in Meena: 28 Mar 2017, 10:57 Tue. Since then the Sun has moved 271.8° round the stars. Vikram Samvat numbers that year 2074; Shaka Samvat numbers it 1939.