Round down time by unit duration.
unit duration.
Rounded down timestamp.
import core.time : hnsecs, dur; immutable t = Timestamp(1234567890); assert(t.roundDown(dur!"seconds"(1)) == Timestamp(1230000000)); assert(t.roundDown(dur!"msecs"(1)) == Timestamp(1234560000));
See Implementation
Round down time by unit duration.