|This article is about an older version of DF.|
Time is an integral part of any simulation, none the least in a simulation as complex as Dwarf Fortress. Time is measured internally in unnamed units, commonly dubbed "ticks" by the community. Each tick represents one step in the Dwarf Fortress program, requiring calculations related to unit movement, fluid movement, temperature transfer, various event checks, combat checks, pathing checks, job changes - basically everything required to run the program, broken up between individual lumps of time. These ticks are then bundled up against days, months, seasons, and then years under the dwarven calendar. For a discussion on the greater passage of time, see Calendar; this page is focused on the lower-level, "unit-based", in-game passage of time.
How much a tick in time is worth against the yearly dwarven calendar depends on the game mode, as time in fortress mode is much more heavily accelerated than it is in adventurer mode. Fortress mode counts 1200 ticks per day and 403,200 per year, while adventurer mode counts 86,400 ticks to a day and therefore 29,030,400 ticks per year. According to these rates, each tick is equivalent to a real-world second in adventurer mode, but 1.2 minutes in fortress mode, making adventurers 72 times faster than your dwarves tick-for-tick. This is intended behavior, as the pacing in fortress mode is much, much faster than when adventuring.
How quickly time appears to pass in your game, especially in fortress mode, has as much to do with your hardware as with the number of ticks in a year. The number of frames per second is a direct reflection of how many ticks a second your processor is working through. This should be distinguished from the frame refresh rate, which is how many frames appear on your screen per second - since there's a limit to how many frame changes the human eye can see, there's not much purpose to displaying every single one of them on-screen. You can set your FPS to be visible by changing [FPS:NO] to [FPS:YES] in your Init.txt file, which will display your framerate in the top-right corner of your game window. By default the framerate is capped at 100 FPS, but this setting can be changed or even removed: see Frames per second#Controlling FPS for a technical discussion. For tips on maximizing framerate, see the (topically named) Maximizing framerate article.
Dwarf Fortress is an extremely processor-intensive game, and so how many frames you actually get per second will depend on the strength of your machine, how far into the game and how clutter there is in it, whether or not you are not taking any fps-saving measures, what mods or other programs you are running, and so on. Regardless of mode, there are 28 days in a month and 12 months in a year. Assuming an FPS of 100, not counting pauses an hour of fortress mode gameplay will translate into a year in-game.
The amount of time in between a creature's actions is at its root directly proportional to its speed. The default base speed is 900, though this value can be changed with a [SPEED:#] creature token in the creature raw files. A median creature with default speed will be capable of performing an action roughly every 10 ticks. The creature's actual performance is subject to many other modifiers (agility, strength, encumbrance, etc.).
Plants use a [GROWDUR:#] plant token to constrain their growth times. Each GROWDUR unit (short for "grow duration) is equivalent to a hundred ticks. The default value is 300 and it is usually set to 300 or 500 (30000 or 50000 ticks) for crops; there are 1008 GROWDUR units per season.
Aging and lifespan