Time distance; Time interval
A span is a directed duration of time. A duration is an amount of time with known length, but no specific starting or ending instants. For example, the duration “1 week” is known to have a length of 7 days, but can refer to any block of seven consecutive days. A span is either positive, denoting forward motion of time, or negative, denoting backwards motion in time.
Concerning the synonyms, the terms “time interval” is generally understood to denote an anchored span in the general community of computer science. Only in the SQL language does “time interval” denote a span. The term “span,” which has only one definition, is thus recommended over “time interval” for works not related to the SQL language. This use is unambiguous.
A “duration” is generally considered to be non-directional, i.e., always positive. The term “time distance” is precise, but is longer.
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