April 30, 2021 4 min read

Why is it different times in different countries, who came up with the idea and when did it start? To understand the concept, picture the Earth rotating as it circles the sun on its yearly orbit. Each 24 hours, the Earth performs one complete rotation, which is why a day is 24 hours long. Whatever your location on the globe it will rotate into sunlight and then into darkness, which we perceive as day and night respectively. If we had one global time zone, noon would be in the middle of the day for some locations, but in the morning, evening or night for others. As humans are naturally most active during daylight hours, this would cause chaos for international business and commerce. It would also have a seriously detrimental effect on the mental wellbeing of a large part of the global population. By dividing the surface of the Earth into 24 time zones, we ensure that noon is as close to the highest point of the sun’s arc for every location.

The origin of time zones

Before the invention of mechanical clocks, sun clocks used the position or length of a shadow cast in daylight to measure time. As the sun is at its highest point in the sky in the middle of daylight hours, this became midday, or noon. Ironically, every location had its own distinct noon before time zones as we now know them were ever imagined. As instant communication with anywhere else was impossible, only local noon was relevant to a given population.

In 1675, the Royal Observatory was founded in Greenwich to study and chart the stars to establish longitude for naval navigation. The 1714 Longitude Act established the Board of Longitude and declared the Greenwich Median the starting point for all British longitudinal measurements. The Naval Ministry established the 24 hour clock and divided the globe into 24 longitude lines. These were 1,000 miles apart at the Equator, or 15 degrees of the Earth’s circumference. Midnight in Greenwich was decreed as 00.00 hours and this time reference named as Greenwich Mean Time (GMT). With the invention of the chronometer in 1764 accurate timekeeping at sea became possible and a ships position could be deduced accurately from this. Due to the sheer volume of British ships at sea (more than all other navies combined) GMT quickly became the dominant time reference.

Despite these developments, local noon still prevailed on land as land travel was still so slow. Travelling between locations took so long that any local time differences were lost on the traveller during the journey. However, in the 19th Century two things would change this: long distance telecommunications and the rise of the railways.

Railway Time

Local solar times made running an accurate and effective rail system inconvenient, if not impossible. Trains could not follow timetables properly if each station had a time inconsistent with others on the same route. Crashes and near misses also became more frequent as the railway system grew and more trains following different local times were employed. In 1840 the Great Western Railway solved this by using portable chronometers set to GMT as time reference on all their trains. This became known as Railway Time and was quickly adopted by other railway companies. Station clocks were equipped with two minute hands, one for local times and one for railway time to aid travellers. By 1855, time signals from Greenwich were being transmitted by electric telegraph along the railway telegraphic network. This allowed accurate timekeeping across the country, based on the new electro-magnetic clock in Greenwich and 98% of towns and cities switched from local time to GMT.

In America, the issue was even more pronounced due to the far greater geographical area served by the railways. With every city in America using a different time standard, there were over 300 local solar times. After a collision between two trains using different local times in New England killed 14 passengers in 1853, it became clear a solution must be found. New England railway schedules were coordinated and a series of further collisions led to the founding of the General Time Convention. This was a committee of railway company representatives set up to agree on a consistent method of scheduling. In 1870, ‘A System of National Times for Railroads’ was published by Charles F. Dowd proposing a single time system for all railways. This met with resistance from rail companies and in 1881 a simpler system of five time zones to replace the 50 different railway times was put forward. On November 18, 1883 four standard time zones were introduced for the continental United States.

The International Meridian Conference

The Greenwich Meridian had been informally recognised as the prime meridian by many people prior to 1884. This was largely due to the accurate and reliable navigational data published by the Greenwich Observatory. The Scottish Canadian engineer Sir Sandford Fleming first proposed a system of 24 worldwide time zones in 1879. He advocated a prime meridian in Greenwich, the adoption of a standard mean time and hourly variations by time zone based on GMT. Five years later he helped to convene the International Meridian Conference in Washington DC. While this did not have the power to introduce the time zones fully, it was agreed that a universal 24 hour day starting at midnight in Greenwich would be introduced. The prime meridian was also to be located in Greenwich as Fleming proposed. This would benefit shipping industries worldwide as the predominantly accepted prime meridian would become standard for all.

By 1900, most countries had adopted a standard time zone, although many still resisted using an hourly offset based on GMT. This took several decades, but by 1929 virtually all countries recognised the time zones we now regard as standard. In 1972, Coordinated Universal Time (UTC) became the worldwide time standard and remains so to this day.

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