UTC−12 is a nautical time zone comprising the high seas between 180° and 172°30′W longitude. Subtract twelve hours from Coordinated Universal Time to obtain the time for this zone. Ships using this time are the last to begin each calendar day.
Characteristics of the time zone which observes UTC-12
A number of inhabited islands lie within the longitudinal limits of this time zone, but none of them keeps the date and time of UTC-12. Instead, they keep the time and date (or just the date) of one of the neighbouring zones, usually because they belong, politically, to an island group whose other members lie mostly in the neighbouring time zone.
Since the IDLW time-zone represents the last place on earth where any date exists, it is sometimes used for deadlines and referred to as Anywhere on Earth (AoE).