Very few people pay attention to the published boarding times. 2 PM is kind of the generic norm and if observed that would give the crew and staff sufficient or at least more time to prepare the ship for the oncoming passengers. Holland America goes as far as to publish boarding times by deck but at the same time extends early boarding to the higher level suite passengers and to passengers with advanced standing in the line’s frequent cruiser program. Depending on the ship and the cruise it’s not unusual to see 50-60+% of the passengers with some kind of priority. On top of that despite publishing the generic kind of 2 PM booking time the lines often start boarding as early as 12:00-12:30 PM. Experienced cruisers know that and those anxious to get on board and start their cruise will show up at the terminal early in the morning. Often means standing outside waiting for the terminal to get disembarking out and gone but apparently worth it for some.