Many astronomy books and magazines give information on astronomical events in Universal Time. It is based on the mean solar time for the meridian at Greenwich, England. That is the time when the sun passes directly over the meridian at Greenwich. The meridian is a true north-south line passing from pole to pole. The Earth is divided into 24 hours by meridians, beginning at the Greenwich, England meridian. It is called Universal Time or Greenwich Time.

Universal Time or UT or UTC is used worldwide by astronomers and other people to avoid confusion between time zones. Like Military Time, it is expressed in the 24-hour system. All morning hours sound the same, but after noon, 12 hours are added to the time. For example, 1:00 p.m. would be 13:00, and 6:30 p.m. would be 18:30.

To convert Universal Time to our local Central Standard Time, subtract 6 hours. To convert UT to our current Daylight Savings Time, subtract 5 hours. If you get a negative number, add 24 hours.