|This article is about an older version of DF.|
Age is a creature attribute describing how long the creature has been alive, including creatures born before the beginning of time in terms of world generation (year zero). Age determines the life stage of creatures and, until it is fully grown, is the most important element of the creature's body size. All creatures have an age associated with them, but in fortress mode only your own dwarves will have observable ages in the thoughts and preferences screen. The age of a creature is probably a floating value (to account for growth throughout the year), but is displayed in the game as an integer that is ticked up every time it reaches a birthday.
The age of a creature has an important effect on its overall size and maturity. The starkest example of this in the game is the case of the dragon, which is born 6,000 cm3 in size (and technically an adult) then takes a thousand years to reach its full size of 25,000,000 cm3. However, the vast majority of the non-sapient creatures your dwarves encounter take one year to mature to adulthood and two years to reach full size; elephants and giraffes are notable exceptions, as their young take ten years to mature (though they reach full size in only 5 years). Upon reaching adulthood, creatures can reproduce, be trained, milked, sheared, revert to wild status, and various other effects.
The life cycle of dwarves is slightly more complicated: juveniles ages zero to one are considered babes, and must be carried about by their mothers; between the ages of one to twelve are they are considered children, and can perform some limited tasks; and once they reach 12 years of age, they are considered adults. The process is the same for other civilized races, the original animal people, and the humanoid semi-megabeasts.
Another aspect that is controlled by age is lifespan. Most organic creatures will eventually die of old age (including fortuitous fortress dwarves), usually within a range of 1-100 years. Giant versions of animals inherit their normally-sized brethrens' lifespans, while animal people usually have somewhat longer lifespans than their representative creatures. A few species, such as elves, goblins, and some unintelligent and unnatural creatures, will live until killed. Megabeasts, the undead, night creatures, and the procedurally generated forgotten beasts and titans are similarly immortal. Immigrants may sometimes show up with incorrect ages (future birthdates) Bug:3945 or incorrect life stages (4 month old children) Bug:3752. This normally does not cause a problem, and life stages get rechecked every birthday. Note that only an intelligent civilized creature vulnerable to death by expiration will seek necromancy, which means goblins and elves never become practitioners of the dark arts.
 Sample list of age characteristics
|Name||Age of Adulthood||Age of Full Size||Minimum Age of Death||Maximum Age of Death|
- [CHILD:#]: Age at which children become adults. Set to 1 for most creatures, up to 10 for a few (giraffe, elephant), and is set to 12 for most sapient creatures.
- [BABY:#]: For sapient creatures, age at which babies become children. Always set to 1.
- [BODY_SIZE:#:#:#]: Controls the body size of the creature, typically two or more are used to constrain its growth pattern. The first number is age in years; the second additional age in days. The third number is its size in cm3. The body size points are independent of the age of adulthood for the animal: many animals are adults in one year, but take two years to reach their full size, for instance.
- [MAXAGE:#:#]: The first number given is the minimum natural lifespan of a creature, while the second is the maximum. The distribution of deaths from natural causes in between the two values is unknown, but likely linear; the moment of death-by-old-age of a creature is stored from birth. If this tag is not present at all, the creature is biologically immortal.