मलयालम् word meaning Day. A story about the origin of day, night, dawn and dusk is contained in विष्णु पुराण . At the time of the great Deluge everything from gods down to the rocks lay submerged in परब्रह्मन् (Supreme Being). ब्रह्मा sat in meditation to initiate what he termed as जगत्सृष्टि , the four species of living beings like the देवस्, असुरस्, पितृस् and men. When the meditation proceeded, the तमोगुण in ब्रह्मा became prominent and so first and foremost of all, the असुरस् were born from his waist. Then ब्रह्मा discarded his तमोगुण and the manifestation of the discarded तमोगुण became Night. ब्रह्मा sat again in meditation and from his face sprang out the देवस् , who were embodiments of सत्त्वगुण . ब्रह्मा discarded the सत्त्वगुण and it then became Day. That is why असुरस् are powerful at night and देवस् by day. Then another manifestation with सत्त्वगुण predominating sprang out from ब्रह्मा and it was called पितृस् . ब्रह्मा discarded that also and it became Dusk. ब्रह्मा sat again in meditation and then were born men who were a manifestation of रजोगुण . ब्रह्मा discarded that also and it then became Dawn. That is why men are strong at dawn and the पितृस् strong at dusk. It is because of these that it is said that day, night, dawn and dusk are bodies of ब्रह्मा . All the above four are an asylum of the three गुणस् .

Night is called उषा and day, व्युष्टि . सन्ध्या (dusk) is the time between उषा and व्युष्टि . When the fierce and terrible सन्ध्या commences, a set of ferocious demons called मन्देहस् desire to eat the Sun. A fight ensues then between the Sun and the demons and by a curse of प्रजापति the demons die daily though their bodies never perish. At that time the best of ब्रह्मिन्स् with the sound of ' ओम् ' vibrating recite the गायत्री and throw water upwards. That water transforms itself into वज्रायुध and burns to death the wicked demons. The first oblation to the sacrificial fire is performed reciting the mantra which begins with "Sūryojyotiḥ". ' ओम् ' is but भगवान् विष्णु , lord of the Vedas with the lustre of ऋक्, यजुस् and साम . The very utterance of the word ' ओम् ' therefore, destroys the demons मन्देहस् . (Chapter 8, Aṃśa 2, Chapter 5, Aṃśa 1, Viṣṇu Purāṇa)