Definitions for "lifespan"
Keywords:  captive, wild, can't, typical, easy
the period of time in which the life events of a species typically occur.
amount of time in the life of an organism. This is not easy to determine for wild animals. The typical or maximum ages reached by captive animals are often better known (and may be the only information available). However, it can't reflect what most wild populations really experience
Keywords:  happy, birth, explained, death, battery
the period during which something is functional (as between birth and death); "the battery had a short life"; "he lived a long and happy life"
In these help pages, a lifespan refers to the combination of the birth date and the death date. Second Site has a few formatting options for lifespans that are explained in the Dates section.
a small, simple program that does it's job very efficiently