Panchang in Chahārbāgh, Alborz Province, Iran Tue 13 Nov 2018

The evening arghya is offered at sunset. Shashthi runs from 23:51 on Mon 12 Nov to 02:22 on Wed 14 Nov, so it holds sunset only on Tue 13 Nov, at 17:01. No text giving Chhath · Sandhya Arghya’s time was found; sunset is Tithika’s convention.

Chhath: every date in Chahārbāgh

The Moon gains on the Sun about 12° a day. Each 12° of lead is one tithi: 60°–72° is the 6th, Shukla Shashthi. A day takes the tithi in force at its sunrise, 06:40 here. Panchami ended at 23:51 Mon, before it. Shashthi ends at 02:22 Wed, when the lead reaches 72°. The lead passed 0° at the new moon of 7 Nov, so the Moon is waxing: Shukla paksha.

The night of Mon 12 Nov ran from sunset 17:01 Mon to sunrise 06:40, 13 h 39 m. Cut into 15 muhurtas of 54 m, its 14th is Brahma Muhurta, the one before the last.

Daylight here, 06:40 to 17:01, splits into 8 choghadiyas of 1 h 17 m. Their names follow a fixed order that starts from the weekday, and each name is counted good, neutral or bad.

The night here, 17:01 to 06:41 Wed, splits into 8 choghadiyas of 1 h 42 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 Ashadha spans 266°40′–280°00′; the Moon entered its pada 1 at 266°40′. It leaves at 03:36 Wed, for Shravana.

Add the Sun's and the Moon's places among the stars: 206.6° + 269.7° = 476.3°, one full turn and 116.3°. Past the turn, cut into 27 parts of 13°20′, it gives the yoga: 106°40′–120°00′ is the 9th, Shula. It ends at 13:41, then Ganda.

A karana is half a tithi: 6° of the Moon's lead, so the first half of Shashthi is Kaulava and the second Taitila. Kaulava runs until 13:04, when the lead reaches 66°; Taitila until 02:22 Wed.

A Hindu day runs from one sunrise to the next, not midnight to midnight. This one runs 06:40 to 06:41 Wed, so the hours after midnight still belong to Mangalawara.

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: Tula gives Kartika. The Sun enters Vrishchika on 16 Nov, inside the month. The next new moon, 7 Dec, finds it in Vrishchika and begins Margashirsha.

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 7 Nov, with the Sun in Tula, began Kartika. This Shukla paksha reads Kartika in both counts.

A samvat year begins with Chaitra, the month whose new moon finds the Sun in Meena: 17 Mar 2018, 16:41 Sat. Since then the Sun has moved 233.8° round the stars. Vikram Samvat numbers that year 2075; Shaka Samvat numbers it 1940.