In Avatar, as Pandora itself is a moon orbiting around a planet, that in turn orbits around a star, does it (Pandora) have random number of hours in day and night? Is there any reference about it?
Pandora receives significant light from Alpha Centauri B (ACB). As a result, Pandoran nights are never dark during half of the Polyphemian year, but instead are more like Earthly dusk. At the closest point in its orbit, ACB is about 2,300 times as bright as Earth's full moon; at its furthest point, it is still one hundred and seventy times as bright. During the other half of the year when ACB is in the daytime sky, many Pandoran nights are illuminated by both Polyphemus's huge disk and the reflected light from other nearby moons. Truly dark nights are uncommon. Polyphemus occasionally eclipses ACB at night for about one hundred minutes, but the light reflected by the planet still keeps the night from being dark.
When ACB shares the daytime sky with ACA, at its closest it adds about half a percent to the total illumination. When the 2 stars are close together in the sky, the effect of ACB's more orange light is unnoticeable. But, as they separate over the years, an orange tint may be seen in areas shadowed from ACA's direct illumination. At its most distant, ACB is about 2,700 times dimmer than ACA and does not produce noticeable lighting effects. However, it still appears as a blindingly-bright tiny orange disk in the sky.
Because of its high axial tilt (29°), Pandora exhibits considerable annual variation in the day-to-night ratio. In addition, its elliptical orbit produces seasonal temperature variations and a range in daytime illumination of about ten percent.