Terraria features a 24-hour day/night cycle that affects the appearance of the world, the spawning conditions of certain monsters, the behavior of monsters and NPCs, blooming of Dayblooms and Moonglows, and many other gameplay elements. The in-game music which plays on the surface is different during the day than at night. The day/night cycle repeats itself after every 24 minutes of gameplay.
The time of day can be inferred by noting the presence of certain monsters that only spawn at day or night, by listening to the in-game music, or by observing the position of the sun/moon in the background (this can be seen when the player is on the Surface, though not in Outer Space or Underground). To determine the time of day directly, items such as the Grandfather Clock, Watch or GPS must be used.
Daytime in Terraria begins with sunrise at 4:30 AM and lasts for 15 hours (15 minutes of gameplay) until the sun sets at 7:30 PM. During the day, the sun travels across the sky from left to right. In surface biomes, the overall spawn rate of monsters is lower during the day than at night.
NPCs can only spawn/respawn during the day--they cannot do so at night.
Daybloom is a flower which only blooms during the day.
Nighttime in Terraria begins with sunset at 7:30 PM and lasts for 9 hours (9 minutes of gameplay) until the sun rises at 4:30 AM. During nighttime, stars can be seen in the background and the moon travels across the sky from west to east. In surface biomes, the overall spawn rate of monsters is greater at nighttime than during the day. Also, a wider variety of monsters can spawn at nighttime, many of which are more dangerous than monsters that typically spawn during the day.
Some monsters such as the Zombie, Demon Eye, Gastropod and Possessed Armor will only spawn at night and will never spawn during the day. Many bosses such as the Eye of Cthulhu, Skeletron and their Hard Mode counterparts can only be summoned or initially encountered at night. When the sun rises, monsters exclusive to nighttime will typically flee and despawn.
At night, Fallen Stars will intermittently fall from the sky until they hit a solid surface, at which point they can be collected by the player. In the unlikely event of a star falling on a mob it will cause a great deal of damage since the base damage for a fallen star is 1000, it only hurts before it hits the ground. After the player has smashed 1 or more Shadow Orbs/Pulsating Hearts, each night presents a very rare chance for a Meteorite to spawn as well.
Each night has a 1 in 9 (i.e. 11.1%) chance to be a Blood Moon, which is a special event where monsters spawn far more frequently. It can be very dangerous for new or unprepared players.
- When a player joins a newly-created world for the first time, the time of day is always set to the default value of 8:15 AM.
- Daytime on the surface is generally far safer than nighttime, due to the type of monsters that spawn and the rates at which they spawn. For this reason, new players are advised to explore the surface during the day and build a house before nighttime for safety.
- Time in the game passes 60 times faster than time in real life. That means that 1 second of gameplay is equivalent to 1 minute in-game, 1 minute of gameplay is equivalent to 1 hour in-game, and 24 minutes of gameplay is equivalent to one day/night cycle (24 hours) in-game.
- At nighttime, when the moon is directly at the top of the screen, the time of day is 12:00 AM (midnight). During the day, when the sun is directly at the top of the screen, the time of day is 12:00 PM (noon).
- The message that appears when summoning a Goblin Army or the Frost Legion appears to be tied to the time of day.
- Skeletron and Skeletron Prime can only be summoned at night, but they will not flee at dawn. Instead, they will gain a ridiculous amount of defense during the day and their attack will be so high that they can kill the player in one hit.
- In the game's title menu and loading screen, you can grab the sun/moon and move it around. This doesn't have any effect on the time of day once you've entered a world.
- Your first night is always a full moon.
- There are such things as non-hostile nights. No monsters spawn on these nights. Any night has a chance to be non-hostile.
- A new message "This is going to be a terrible night" appears some nights, indicating that The Twins will spawn.
- A new message "You feel the air around you getting colder" appears some nights, indicating that Skeletron Prime will spawn.
- A new message "You feel vibrations from deep below" appears some nights, indicating that the Destroyer will spawn.
- The frame skip glitch (choosing Settings -> Video -> Frame Skip: Off and minimizing the application in your taskbar during gameplay) no longer works. Time now progresses at a normal rate.