Second dog watch

Second Dog Watch also called Last Dog Watch: 1800 to 2000

is a Union Naval Term describing a Watch Period aboard a Union Starship.

A watch system, watch schedule, or watch bill is a method of assigning regular periods of work duty aboard ships and some other areas of employment. A watch system allows the ship's crew to effectively operate the ship 24 hours a day for the duration of long voyages or operations.

When the Union Navy was being formed, many things that would become it's traditions came from Pre Astro Terran aquatic navies, in particular that of the Royal Navy One of those traditions was watchstanding and the division of the day into regular watches

The Standard Union Day (24 hours) is divided into 7 watches:

The senior bridge officers will normally rotate through the watchkeeping schedule, but any officer may be in command for the watch.