Moon phase

The Moon in Terraria moves through a cycle of eight different phases, with the next consecutive phase appearing each night. The current moon phase is indicated by the amount of it that is visible each night. The phase of the moon affects which items certain NPCs sell, as well as certain enemy spawn rates. The first night of a newly created world is always a full moon. Each moon phase starts at 4:30 AM game time the day before the night when that moon will appear, so NPCs that only sell items in a certain moon phase will start selling those items the day before.

It takes only eight in-game nights for the Moon to move through all of its phases. The different phases include the full moon, where the entire circular moon is visible; and four nights later, the new moon, where no moon is visible. Another four nights later, the full moon returns.

Because of how time works in Terraria, nights last 9 real-life minutes, from 7:30 PM game time to 4:30 AM game time.

A Blood Moon can occur during any moon phase except for a new moon. A Pumpkin Moon or Frost Moon can be summoned by the player on any night.

Phase-dependent
The following table details items and occurrences that depend on particular moon phases.
 * * Available the day after the stated Moon Phase
 * ** Requires Angler
 * *** Shirt and pants only
 * **** Available during the night of and day after the stated Moon Phase

History
月相 Phase Lunaire