Calculation Methodology

Method reviewed: 2 October 2026

Each of the 30 supported locations uses a stored city-centre reference coordinate. The calculator does not request precise device location. The selected civil date is interpreted in Asia/Kolkata (IST, UTC+05:30), and displayed clock times stay in IST even if the visitor is outside India.

Using city-specific coordinates matters because sunrise and sunset are solar events. Two cities can share the same time zone while still having different solar times.

The site uses the bundled Astronomy Engine 2.1.19 library to search for sunrise and sunset around the selected city and date. The implementation uses the library’s standard horizon/refraction model. Terrain, elevation, weather and different astronomical definitions can cause small differences from another source.

The deployed calculator is self-contained for the astronomical computation; it does not need a live price API or remote calculation API to return the seven timing categories.

Local daylight from sunrise to sunset is divided into eight equal intervals. The weekday chooses which interval belongs to each category.

This is why a fixed chart built around a permanent 6:00 AM sunrise and 6:00 PM sunset is only an illustration. The actual interval length changes with real daylight.

Abhijit Muhurat: the implementation normally uses the eighth part of a fifteen-part division of daylight and does not display Wednesday as an auspicious Abhijit period under this site’s convention.

Brahma Muhurta: the implementation uses the actual night from the previous sunset to the selected sunrise, divides that night into fifteen equal parts, and uses the two parts immediately before sunrise according to the site’s chosen convention.

Dur Muhurtam: the site applies a weekday table using fifteen-part daytime or nighttime divisions. Some weekdays have two periods; Tuesday can include a nighttime period.

Amrit Kaal is not derived from the same daylight-eighth method as Rahu Kaal. The calculation follows the Moon’s nakshatra timing using the implementation documented in the project, including a Lahiri sidereal framework and a sunrise-to-next-sunrise Panchang day. Depending on the date, the page can show one or more intervals or explain that no interval overlaps the selected Panchang day.

A missing interval is not replaced with a fabricated time.

Displayed times are rounded to the nearest minute while internal calculations retain more precise timestamps. Because start and end labels are rounded independently, the difference between the two displayed clock labels can occasionally differ by one minute from the displayed duration.

Regression tests cover all 30 supported cities across a set of normal dates, leap dates, weekday patterns and boundary cases. Selected public Panchang reference points are also used as cross-checks. These tests improve consistency but do not make every Panchang tradition identical.

The site’s implementation has been cross-checked against documentation for Astronomy Engine and public explanations of the Rahu Kaal convention at Drik Panchang. External references are provided for transparency; their content can change independently of this site.