pm was a designation for time in the latter half of the Earth day, beginning at noon and ending at one minute before midnight.
In Shannon O'Donnel's 31 December 2000 journal recording, she noted that it was 11:15 pm. (VOY: "11:59")
In 2374, while trapped in the Hirogen World War II simulation, Tom Paris recalled "August 29, 1936, 12.17 p.m." as being the time that is train pulled out of Sainte Claire, and the last time her ever saw Brigitte. (VOY: "The Killing Game")