Time Zone (TZ)

A geographic or administrative region using the same civil-time offset from Coordinated Universal Time.

Time zones are commonly expressed as UTC plus or minus a number of hours and sometimes minutes. Governments define civil zones and daylight-saving changes, while marine forecasts, radio schedules, tide tables and logbooks may remain in UTC or another explicitly stated time.

A location name or longitude alone does not always determine legal time, and offsets can change. Navigation calculations and records should retain date, zone and daylight-saving status, particularly when converting predictions or crossing midnight and the International Date Line.