Panchang in Chahārbāgh, Alborz Province, Iran Mon 1 Aug 2016

Shiva’s worship centres on nishitha, the midnight muhurta. Chaturdashi runs from 03:42 on Mon 1 Aug to 02:14 on Tue 2 Aug, so only Monday night’s nishitha (00:53 Tue–01:33 Tue) falls within it. No text giving Masik Shivratri’s time was found; nishitha is Tithika’s convention.

Masik Shivratri: every date in Chahārbāgh

The Moon gains on the Sun about 12° a day. Each 12° of lead is one tithi: 336°–348° is the 29th, Krishna Chaturdashi. A day takes the tithi in force at its sunrise, 06:14 here. Trayodashi ended at 03:42, before it. Chaturdashi ends at 02:14 Tue, when the lead reaches 348°. The lead passed 180° at the full moon of 20 Jul, so the Moon is waning: Krishna paksha.

The night of Sun 31 Jul ran from sunset 20:11 Sun to sunrise 06:14, 10 h 3 m. Cut into 15 muhurtas of 40 m, its 14th is Brahma Muhurta, the one before the last.

Daylight here, 06:14 to 20:11, splits into 8 choghadiyas of 1 h 44 m. Their names follow a fixed order that starts from the weekday, and each name is counted good, neutral or bad.

The night here, 20:11 to 06:15 Tue, splits into 8 choghadiyas of 1 h 15 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′. Punarvasu spans 80°00′–93°20′; the Moon entered its pada 1 at 80°. It leaves at 01:08 Tue, for Pushya.

Add the Sun's and the Moon's places among the stars: 105.2° + 82.5° = 187.7°. The sum, cut into 27 parts of 13°20′, gives the yoga: 186°40′–200°00′ is the 15th, Vajra. It ends at 02:23 Tue, then Siddhi.

A karana is half a tithi: 6° of the Moon's lead, so the first half of Chaturdashi is Vishti and the second Shakuni. Vishti runs until 14:55, when the lead reaches 342°; Shakuni until 02:14 Tue.

A Hindu day runs from one sunrise to the next, not midnight to midnight. This one runs 06:14 to 06:15 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: Mithuna gives Ashadha. The Sun enters Karka on 16 Jul, inside the month. The next new moon, 3 Aug, finds it in Karka and begins Shravana.

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 3 Aug, with the Sun in Karka, begins Shravana. Until then this Krishna paksha reads Shravana here, and Ashadha in the amanta count.

A samvat year begins with Chaitra, the month whose new moon finds the Sun in Meena: 7 Apr 2016, 15:53 Thu. Since then the Sun has moved 111.2° round the stars. Vikram Samvat numbers that year 2073; Shaka Samvat numbers it 1938.