It was on November 18, 1883 that all U.S. railroads set their clocks to use the same standard time. Before then each railroad set their clocks to the time of the railroad's major city. There may have been a difference of over 20 minutes between these and getting connections was frustrating for passengers. Travelling in a train from New York might mean you would arrive at 1:55, but the 2 o'clock train from another part of the country might actually leave at 2:20 New York time. To avoid confusion with a.m. and p.m. a 24 hour clock was eventually adopted.Time Zones before 1883 were not used and even within the same state there could be 2 minutes or more difference between towns.
The International Meridian Conference at Washington DC, USA, adopted a proposal in October 1884. The proposal stated that the prime meridian for longitude and timekeeping should be one that passes through the centre of the transit instrument at the Greenwich Observatory in the United Kingdom (UK). The conference therefore established the Greenwich Meridian as the prime meridian and Greenwich Mean Time (GMT) as the world’s time standard. The international 24-hour time-zone system grew from this, in which all zones referred back to GMT on the prime meridian.
The main factors that favored Greenwich as the site of the prime meridian were:
- Britain had more shipping and ships using the Greenwich Meridian than the rest of the world put together (at the time). The British Nautical Almanac started these charts in 1767.
- The Greenwich Observatory produced data of the highest quality for a long time.
