A pair of Tempo values denoting an inclusive range, produced by the ISO 8601-2 range operator (..) inside a set — [1667,1670..1672] (one of 1667, 1670, 1671, or 1672) or {1M2S..1M5S} (ISO 8601-2 §6.4). Both bounds are inclusive — contrast with %Tempo.Interval{}, which uses the half-open [from, to) convention.

A range is a member-level element: it appears inside a Tempo.Set.t/0 (and in ~o sigil match patterns), never as a top-level parsed value, and it is not an operand of the interval algebra — the enclosing set's own expansion and certainty machinery interpret it. Open-ended ranges are represented by :undefined on either endpoint ([1760-12..] — December 1760 or later).