Significance of Length of day
The keyphrase "length of day" encompasses various interpretations, as discussed in both Purana and Indian history. In Purana, it signifies the passage of time affecting a bird's strength, the advanced age of a vulture, a promise of longevity by a king, and a blessing of extended life from a divine source. In Indian history, "length of day" is understood through different cultural measurements, including Persian and Sanskrit terms, focusing on the duration from sunrise to sunset.
The below excerpts are indicatory and do represent direct quotations or translations. It is your responsibility to fact check each reference.
Hindu concept of 'Length of day'
In Hinduism, "Length of day" symbolizes promises of longevity and prosperity, reflects the impact of time on strength, indicates advanced age leading to weakness, and signifies a divine blessing of extended life from the 'mighty Father.'
From: Ramayana of Valmiki (Griffith)
(1) The phrase 'length of days' refers to the extended duration of life, which the person received from the 'mighty Father' as a blessing.[1] (2) The king swore by him whose right is length of days, implying a promise of longevity, perhaps referring to a long and prosperous reign.[2] (3) This indicates the advanced age of the vulture, which is contributing to the weakening of its strength and its ability to fight.[3] (4) This refers to the passage of time and its effect on the bird, which has diminished his strength and capabilities.[4]
From: Hayanaratna: The Jewel of Annual Astrology
(1) The duration of daylight, which is one of the aspects of the year to be written in the annual horoscope.[5]
The concept of Length of day in local and regional sources
The keyphrase "Length of day" pertains to the varying methods of measuring daylight across traditions, including the time from sunrise to sunset, and is described using terms like ruz in Persian and vasara in Sanskrit.
From: History of Science in South Asia
(1) The length of day, called ruz in Persian and dina-ratri or vasara in Sanskrit, is measured differently by various traditions, such as from the rising of the center of the disc of the Sun until its setting, or from the rising of the true dawn until the setting of the entire body of the Sun, or from dawn to the time of the setting of the disc of the Sun.[6]