Markandeyapurana 48.14

48.14

jyotstanā sandhyā tathaivāha---sattvamātrātmakaṃ trayam /
tamomātrātmikā rātriḥ sā vai tasmāt triyāmikā //

Thus these bodies of the wise God of gods have become famed as the night and day, and the evening twilight and the morning twilight, O brāhman. Three are characterized by the particle of goodness, namely, the morning twilight, the evening twilight and the day; the night is characterized by the particle of darkness, hence it is called Tri-yāmikā.[4] Hence the gods are powerful by day, but the Asuras by night, and mankind at the coming of the morning twilight, and the pitṛs at the evening twilight. At these times these classes of beings are undoubtedly powerful and unassailable by their foes; and when they light upon the adverse times they lose their power.