Period.of constructor
Creates a period of a given duration containing at.
Implementation
factory Period.of(
Duration duration, {
required DateTime at,
}) {
assert(duration != Duration.zero, 'Duration must not be zero.');
const microsecond = Duration(microseconds: 1);
return duration.isNegative
? Period(start: at.add(duration + microsecond), end: at)
: Period(start: at, end: at.add(duration - microsecond));
}