North Pole has no local time

In most places in the world Local time is determined by longitude. Thus, the time of the day are more or less synchronized with the position of the sun in the sky (e.g., midday sun is approximately at a maximum elevation above the horizon). However, this system does not work at the North Pole, where the sun rises and sets only once a year, and all lines of longitude, and therefore the time zones crossed.

Since the North Pole people live permanently, the North Pole was not ascribed to any a particular time zone. Polar Expedition used at any time in its sole discretion, for example, Greenwich Mean Time, or the time zone of the country from which they came.

via factroom.ru