Day and night cycle



The day and night cycle of the Terraria world refers to the rising and setting of the Sun and Moon, and the ways this can affect the world.
 * Day begins at 4:30 a.m., while night begins at 7:30 p.m.
 * Day and Night each have their respective theme music in some surface biomes.
 * Some surface enemies only spawn at night (see Enemies below).
 * Some NPCs sell unique items at night, like the Arms Dealer, who sells Illegal Gun Parts at night.

Note that the sun in Terraria rises at the left of the map, even though the left is referred to in-game as "West" (the same for right/East), e.g. when a Goblin Army, Frost Legion, or Pirate Invasion begins approaching.

Time

 * All newly-created worlds begin at 8:15 a.m.
 * One minute of in-game time lasts one second of real-world time, meaning one hour in-game lasts one minute real-world. One Terraria day, therefore, lasts 15 real-world minutes, and night lasts 9 real-world minutes.
 * In-game time can be displayed with the following:
 * Any placed Grandfather Clock will display the current hour for all players within ~80 tiles horizontal and ~50 tiles vertical of the clock. Using the key on it displays the exact time in a status message.
 * On, having a Gold/Platinum Watch, GPS, , or in the player's inventory displays the exact time (the Tungsten/Silver Watch and Tin/Copper Watch will display time to the nearest in-game half-hour and hour respectively).
 * colors the character's hair dependent on the time, providing a rough estimate.
 * Using the, time can be sped up to the end of the current cycle (i.e. to 4:30 a.m.) once every seven days.

Enemies
At the surface layer, unique enemies spawn at night. Nocturnal enemies will run or fly away when the day starts.

Additionally, Eye of Cthulhu, Skeletron, The Twins, The Destroyer, Skeletron Prime and can only be summoned at night. In contrast, King Slime can only spawn randomly during the day, though it can be summoned with the Slime Crown at any time.

The following enemies only spawn during the night:

Naturally, all enemies exclusive to a Blood Moon also only spawn at night.

Trivia

 * On the title screen, the sun or moon can be dragged around.
 * Before formal server software was released for Terraria, and while it was necessary to open a second window of Terraria to host a server, dragging the sun or moon around would directly change the time of day within the server.
 * While wearing sunglasses, the sun appears to be wearing them as well. Un-equipping the sunglasses will cause it to revert. This has no functional effect.
 * Internally, the time counter is reset to zero at both dawn and dusk. During daytime, the counter is allowed to go up to 54000, and during nighttime, it is only allowed to go up to 32400.
 * Despite the sun and moon both always being on opposite sides of the sky, there are still moon phases (there can be a new moon even though the moon is not visible).
 * Hopefully, they will add sun phases in future updates.