A dog watch is a work shift, also known as a "watch", in a maritime watch system that is half the length of a standard watch period. This is typically formed by splitting a single four-hour watch period between 16:00 and 20:00 (4 pm and 8 pm) to form two two-hour dog watches, with the "first" dog watch from 16:00 to 18:00 (4 pm to 6 pm) and the "second" or "last" dog watch from 18:00 to 20:00 (6 pm to 8 pm).