In addition, time zones are important for military operations. Communication becomes much easier when both parties are in the same time zone. It is very important to note that times zones are very useful for commerce because they help countries that are close to each other to keep the same time. The difference is expressed as either UTC- or UTC+ and the number of hours and minutes. For UTC, time changes 1 hour forward and backward equivalent to a 1-hour difference in mean solar time for every 15 degrees east or west of the prime meridian( with a longitude of zero degrees) in Greenwich, United Kingdom. The local time within a time zone is defined by its difference from Coordinated Universal Time (UTC): the world’s time standard. In other words, all the countries in a time zone keep the same time. Since that time, the different time zones have always been calculated based on their relation to the UTC.Ī time zone is basically a region of the globe where the same standard time is used. However, in 1972, Coordinated Universal Time ( UTC) became the world’s time standard, replacing the GMT. never became compulsory until March 19, 1918, when Congress passed the Standard Time Act. Therefore, all time zones in the world referred to the GMT zone and the prime meridian to ensure a fully synchronized time standard, giving us what we have now: the 24-hour international time zones.Īfter the adoption of the GMT by the International Meridian Conference, some states in the United States began to use the time zones. Additionally, the 24 time zones would be based on this location (Greenwich, England, was agreed to be the prime meridian, which refers to zero degrees longitude). Then in 1884, at the International Meridian Conference in the United States, it was unanimously decided that Greenwich, England, would act as the Earth’s prime meridian and the Greenwich Mean Time ( GMT) as the entire world’s time standard.
One of the drawbacks of the pendulum clock, however, was that it could not accurately measure time for scientific purposes and could not also sufficiently determine longitude at sea. The sun was used to measure time, with people telling the time using sundials.Īs time went by, and around the 17th century, some other tools such as pendulum clocks came onto the scene.
An example of these large clocks was the Time Bell (Zytglogge Tower) in Switzerland. What usually was the ‘standard’ was, in many cases, a clock tower or large clock placed in strategic places in these locations where everyone could see it. In the United States alone, there were more than 300 local times during this period. Time varied across short distances, and there were no time standards. A few centuries ago, every country, city, and town of the world was actually on its own time.