How is zone time converted to UTC?

Zone time is converted to Coordinated Universal Time (UTC) by recognizing that the Earth is divided into time zones, each of which typically spans 15 degrees of longitude. This division is based on the Earth's rotation of 360 degrees over a 24-hour period, meaning that each hour corresponds to a movement of 15 degrees.

To convert a specific zone time to UTC, you first determine the longitude of the zone in question. By dividing this longitude by 15, you identify how many hours you need to adjust the time. If the zone is to the east of the prime meridian, you add the calculated hours to the local time, whereas if it's to the west, you subtract those hours.

This method ensures you are accounting for the Earth's rotation and the specific position of the time zone relative to UTC. Understanding and using this system is crucial for accurate navigation and timekeeping, which is essential in maritime operations. The other choices do not accurately represent the relationship between zone time and UTC conversion based on the Earth's longitude.