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Aharmana In Hindu Astrology – Calculation Of Day Time in Hinduism

Aharmana is the duration of a day in Hindu astrology. The duration of a day is the difference of time between sunrise and sunset. Ratrimana is the duration of night in 24 hours minus dinamana.

Dinamana given in panchangas (almanacs) relates to the true sunrise and sunset and apparent sunrise and sunset. True sunrise means the sun touching the horizon and apparent sunrise or sunset means the visibility of the Sun due to refraction so that the sunrise appears earlier and sunset appears slightly later.

The celestial longitude of the Sun, as given in ephemeris, pertains to the center of the sun’s disc while the sunrise and sunset are taken from the upper limb of the Sun. Thus, the true and apparent dinamana differs by four or five minutes at the Tropic of Cancer of nearby.

Thus, sunrise and sunset decide dinamana, and as sunrise and sunset depend on geographical latitude of the place and the sun’s declination on the date of observation. The sun’s declination is zero on March 21 and September 22 ever year, when the sun is on the equator and the declination is +ve and –ve maximum of 23-27 degrees N and 23-27degrees S on June 21 and December 21, as seen in the northern hemisphere. Therefore, on the northern latitude, on June 21, the day will be the longest and on December 21, it will be the shortest; on March/September 21 it will be of 12 hours duration.

The sunrise and sunset are the same for a given latitude in local time, but the use of standard longitudes will change the different zonal standard times. Yet, dinamanas measured in local and standard times will be the same.

Dinamana is useful for every day. The religious activities of days are based on the division of days for example, Pratahkala. True hora, yama (prahara) and muhurtas (auspicious hours) are determined by dividing dinama: by twelve for hora, by four for yama, by fifteen for muhurtas. True mid-noon is decided by diving the day duration by two.