Sleeping arrangements began with multi-day voyages

When did ships first include planned sleeping arrangements?

As soon as ships were designed for multi-day voyages at sea, with hammock points serving as an early planned system.

The answer depends on what counts as a planned arrangement. Wooden warships had assigned points for stringing hammocks even without fixed bunks. Earlier Phoenician, Greek, and Roman vessels often pulled ashore so crews could sleep on land. The meaningful transition therefore came with ships designed for multi-day voyages that required crews to sleep aboard while remaining at sea.