Abhijit Muhurat today in London

A muhurta is a division of the day. The time from sunrise to sunset is split into fifteen equal muhurtas, and the eighth, the one in the middle, is Abhijit. On a 12-hour day it is 48 minutes long and falls around noon by the Sun, which is not 12:00 on the clock in most places.

Many people use it as a general-purpose good time: a window to begin a journey, a new task or a ceremony when the Panchang of the day is otherwise unhelpful. Some traditions do not use it on Wednesdays.

It follows the position of the Sun, so the clock time depends on how far east or west a city is within its time zone and on the season. Delhi and Mumbai share one clock, but their Abhijit Muhurat starts about 17 minutes apart.

The Brahma Muhurta is a different window: the muhurta that ends one muhurta before sunrise, about 96 to 48 minutes before it. Tradition values it for study, meditation and prayer. It is shown on the pages of each city next to the Abhijit Muhurat.

London is far north, so its summer days are very long and its winter days short, which stretches and squeezes every Panchang period; it also changes its clocks in March and October.

Sunrise, sunset, moonrise and moonset come from the Navamsha astrology API; where it is not available they are computed by our own engine, which agrees with it to a fraction of a second. The moment each tithi, nakshatra, yoga and karana ends is computed by that engine from the positions of the Sun and Moon (NASA JPL DE421 ephemeris) in the sidereal zodiac with the Lahiri ayanamsa. Rahu Kaal, Choghadiya, Hora, Abhijit Muhurat and the other periods are fixed fractions of the day worked out from sunrise and sunset.

Almanacs differ in how they define sunrise. Here the Sun rises when the centre of its disc is on the horizon, with no allowance for refraction. Almanacs that use the Sun's upper edge and refraction show sunrise a few minutes earlier and sunset a few minutes later, and their Rahu Kaal and other periods move with it. For a ceremony, follow the Panchang your family priest or local temple uses.