Matsyapurana 124.89

124.89

madhyāhnastrimuhūrtastu tasmātkālādanantaram
tasmānmadhyaṃdinātkālād aparāhṇa iti smṛtaḥ //

One muhûrta consists of 30 kalâs, and a day has 15 muhûrtas. The day increases or decreases as the twilight muhûrtas increase or decrease, owing to difference of three muhûrtas in the course of sun’s journey through the line (equatorial), etc. (The day is divided into five parts, each of three muhûrtas). The first three muhûrtas is Prâtaḥ (morning), the next three muhûrtas, is known as Saṃgava. Three muhûrtas after that is called the Madhyâhna (noon) and a similar number of muhûrtas after it bring about the afternoon called aparâ by the sages; this is followed by evening (Sâyam) of the last three muhûrtas. The day is of fifteen muhûrtas on the equator.—84-91.