fromDuration

auto d = 4.dur!"msecs";
auto t = fromDuration(d);
assert(t.value(milli(second)).approxEqual(4));

auto t2 = 3.5 * minute;
auto d2 = t2.toDuration;
auto s = d2.split!("minutes", "seconds")();
assert(s.minutes == 3 && s.seconds == 30);