Originally Tor'bel had a standard day cycle of 12 hours of daytime, followed by 12 hours of nighttime.
This caused Tor'bel to have two different ways of life. During the day, the Specters ruled the lands and the laws of the land were obeyed. During the nighttime, the Specters slept and Tor'bel became a lawless land filled with sin.
When the Specters discovered that Tenebra was being studied by Noir and Nafaq, they granted eternal light upon the lands of Luminous. By focusing more upon Luminous, they removed the daytime from the rest of Tor'bel, giving only Dusk, Dawn, and Night.
In order to maintain control over Luminous the Specters would each spend one third of the day awake, while the other two slumbered. This weakened the Specters and eventually allowed them to be overthrown by Noir.