Prior to standardization, there were thousands of local times around the world, generally based on the Sun’s position at a given time. Even after clocks became somewhat commonplace, two cities a short distance apart sometimes had very different ideas about what time it was at any given moment. Usually, the accepted time for a given city was based on a well-known clock in the town, like a clock tower, which was often at least partially based on the Sun’s position.
Once people began to
travel, establishing a universal time became more important.
During 1675 the GMT was invented at the Royal Observatory at
Greenwich, England. As transportation and communication
continued to advance, the need to have standard timekeeping
became increasingly apparent. During 1840, the Great Western
Railway in Great Britain adopted GMT (Greenwich Mean Time) as
the standard for its schedule, and by 1847, all British rail
companies were using GMT, which was also called Railway Time.
The Royal Observatory
began telegraphing time signals in 1852, and by 1855, 98% of the
public clocks in Great Britain were displaying GMT, either alone
or in conjunction with local time.
Sir Sandford Fleming
was the instigator of a single, worldwide system of timekeeping.
His basic idea of having a universal day beginning at Greenwich
was ultimately adopted at the International Meridian Conference
in 1884. The conferees decided that the line of longitude that
passed through Greenwich would be the prime meridian where each
universal day would begin at midnight.
As had once been the
case in Europe, and for some semblance of standardization from
town to town, railroad companies set their own times, which
differed from company to company. William F. Allen’s proposal
was adopted by the US rail system on November 18, 1883. It was
called the day of two noons, every railroad station clock was
reset to reflect new time zones, which were designated
Intercolonial, Eastern, Central, Mountain, and Pacific.
Less than one hundred
years ago, the US Congress passed the Standard Time Act in 1918,
which established a single, standard system of timekeeping for the
entire country and designated its five time zones by reference to
the Greenwich meridian.
Incidentally, it is
called “Greenwich Mean Time,” because the Earth’s daily
rotation time is slightly irregular, causing a variance of
about plus or minus 16 minutes, so to be consistent, the
mean time is used.