Pirate Time (or PT; also known as game time or GT) is the American Pacific Time zone, and is the standard that is used throughout the game to schedule events. It provides a single reference time for pirates from different time zones to refer to, and can be viewed via the info command.
Note that Pirate Time follows Daylight Saving Time.
Blockade scheduling and daylight saving time
Blockades begin 24 hours after the chest is dropped. This is not adjusted for the change to or from Daylight Saving Time. If a chest is dropped at noon Pirate Time on the Saturday of the beginning of Daylight Saving Time (in the spring), the blockade will begin at 1:00 pm Pirate Time that Sunday. Likewise, if a chest is dropped at noon Pirate Time on the Saturday of the end of Daylight Saving Time (in the fall), the blockade will begin at 11:00 am Pirate Time that Sunday.