Function: lastCoveredInstant()
lastCoveredInstant(
span):Instant
Defined in: time/format.ts:101
The last moment a half-open span [start, end) actually covers — end itself is the boundary
after the span, one millisecond past its last covered moment. Instant arithmetic only, so it
takes no time zone: end − 1 ms is the same subtraction in every zone.
Takes the whole span, not end alone, because a zero-length span (end === start) has no
millisecond before its own start to name — end - 1 there reads as one moment earlier than
start (#240). A zero-length span answers its own end unchanged instead. start may be
absent (no paired start Field value yet); the zero-length check then never fires.