UTC breaks time into days, hours, minutes, and seconds, where days are usually defined in terms of the Gregorian calendar. Most time zones that are on land are offset from UTC. UTC is not dependent on daylight saving time (DST), though some countries switch between time zones during their DST period, such as the United Kingdom using British Summer Time in the summer months. UTC, which is based on highly precise atomic clocks and the Earth's rotation, is the new standard of today. Although GMT used to be a time standard, it is now mainly used as the time zone for certain countries in Africa and Western Europe. Although GMT and Coordinated Universal Time (UTC) essentially reflect the same time, GMT is a time zone, while UTC is a time standard that is used as a basis for civil time and time zones worldwide. Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory located in Greenwich, London, considered to be located at a longitude of zero degrees. They are often based on the boundaries of countries or lines of longitude. Related Time Calculator | Date CalculatorĪ time zone is a region on Earth that uses a uniform time.