The most obvious thing about the Shepherd gate clock is that it has 24 hours instead of the usual 12 hours. Therefore, the 12 o’clock hour hand is pointing down rather than upwards. The advancement of telecommunication technologies influenced the creation of an even more precise system of time identification. In particular, the concept of Coordinated Universal Time (UTC) was designed to provide a more accurate timekeeping system. Although UTC and GMT indicate the same time, UTC is based on the more precise mechanism of time measurement.
- Since GMT is not a standard time that has an offset from UTC, converting it to other time zones can be a little bit more complicated.
- Although the three terms are used interchangeably, there are small differences in meaning.
- Greenwich Mean Time is the “mean” of the everyday time in the year when the Sun crosses the Prime Meridian at the Royal Observatory Greenwich.
- Even though UTC was introduced as a more accurate time standard, the occurrence of the leap seconds demonstrated that even this system has minor flaws for the universal time synchronisation.
- In 1925 GMT was adopted by astronomers so that the astronomical day began at midnight, the same time as the civil day.
A number of other countries around the world also use this daylight savings measure and change their local times to take advantage of earlier sunrises. In the winter months, local time in the UK is the same as GMT, but in March, local time is moved forward one hour to British Summer Time (BST) until the end of October. West of the Greenwich Meridian, local time is behind GMT (e.g. local time in New York is GMT -5 hours in winter and GMT -4 hours in summer). Generally, if you are in a country east of the Greenwich Meridian, your local time is ahead of GMT (e.g. local time in China is GMT +8 hours).
Current Greenwich Mean Time (GMT)
Besides, considering the growing differences between time of day and clocks, the need for a new system of timekeeping will be needed in the future 10. Nevertheless, UTC still remains to be the most common universal standard of time for all countries. The history of GMT started with the decision of the International Meridian Conference in 1884 to establish the prime meridian which would denote the international standard of time. Considering that Great Britain was a developed marine nation, it used Greenwich Meridian to position own ships. Subsequently, Greenwich meridian was determined as zero degrees longitude, thus, the international standard time2. From that point, every nation used GMT to calculate the time in relation to this standard.
The Differences Between GMT and UTC
For astronomical purposes, the GMT day was said to start at noon and run until noon the following day. This made it easier for astronomers because they could log their observational data (taken overnight) under a single calendar date. When everyone switched to the midnight-based convention in the 1920s and 1930s, this midnight-based time standard was advanced markets review 2021 given the new name of Universal Time to avoid any confusion. When you read weather forecasts and maps, you may notice a four-digit number followed by the letter “Z” somewhere at their bottom or top. The way Greenwich Mean Time (GMT) works is a little bit different from standard time zones such as EST or PST or daylight time zones such as CDT or EDT.
GMT was officially adopted by Great Britain in 1847 when the Railway Clearing House started using it. During Daylight Saving Time, clocks in the United Kingdom are set forward one hour to British Summer Time (BST). Some other countries, such as Ireland, observe the same local time, but under a different name. Initially, the Shepherd gate clock showed astronomical time according to which the counting of the 24 hours of a day starts at noon. The clock was changed to GMT and from this time the counting of 24 hours started from international council of air shows midnight.
British mariners started keeping at least one chronometer set to GMT. This meant us bond auction will test if yields are high enough for buyers they could calculate their longitude from the Greenwich meridian (longitude 0° by convention). But each day measured by a clock has the same length, equal to the average (mean) length of a solar day. It’s a way of standardising and regularising time so we can all know exactly what time it is for our (or anyone’s) location.
What is Greenwich Mean Time
UTC, while based on zero degrees longitude, which passes through the Greenwich Observatory, is based on atomic time and includes leap seconds as they are added to our clock every so often. UTC was used beginning in the mid-twentieth century but became the official standard of world time on January 1, 1972. Eventually, GMT became the unified standard for the economic interactions between countries around the world. The advancement of the technologies of the wireless telegraph indicated that all countries require precise time standard. As a result, in 1911, the International Congress on Astronomical Ephemerides agreed to use GMT for the universal offset of the clocks for other nations.
United Kingdom
There are many major cities in the GMT time zone and in the GMT+1 times zone (Daylight Saving Time). This time ball was a large painted sphere that was dropped at predetermined times to give ship navigators an opportunity to calibrate their chronometers at sea. A modern day example of such a time ball is the iconic Times Square Ball that has been used every New Year’s Eve since 1907 in New York City to signal the onset of the New Year. Today there are still sixty time balls to be found around the world, though most of them have been decommissioned. As the reference for GMT, the Prime Meridian at Greenwich therefore became the centre of world time and the basis for the global system of time zones.