Minecraft wiki entry for Moon, associated text: One Minecraft lunar cycle (from full moon to full moon) takes 2 hours and 40 minutes of playtime. This means there are approximately 9 lunar cycles in one real-world day (24 hours) of play.
Unlike the real-world moon, the Minecraft moon is fixed in the sky relative to the stars, and always opposite to the sun. Therefore, solar eclipses are impossible in Minecraft, and lunar phases should be impossible, but its phases appear as if lit from the north or south.
Standing or flying at a height above the terrain of approximately 1.4× the render distance, the sun appears opposite to the moon in the sky, making it seem almost as if the player is in space.
The star pattern is based on a seed, but not the current world's seed. Like the bedrock pattern, the stars are always based on the same seed, regardless of the world seed.
There is a patch of the full moon that is off color, being 606978 instead of 60687A. This can be found 1 4x4 patch above the bottom right corner.