It didn't happen often, but it has happen in both spoken dialogue and the time displays in some of the earliest episodes. In them, the time occasionally is referred to as, e.g., 1300 hours. Navy people don't do this! (I have a copy of the US Navy's Bluejackets Manual, and have a son who has been in the Navy for approximately a year now.) Navy people would say, "1300", without the "hours" designation added on. (I believe the Army and Air Force do use the "hours" designation, however.)

Navy people say it is a way to pick out landlubbers...