In past centuries, time keeping was a purely local phenomenon. Each town would set their clocks to noon when the sun reached its zenith each day. A clockmaker or town clock would be the "official" time and the citizens would set their pocket watches and clocks to the time of the town, enterprising citizens would offer their services as mobile clock setters, carrying a watch with the accurate time to adjust the clocks in customer's homes on a weekly basis. Travel between cities meant having to change one's pocket watch upon arrival. Once railroads began to operate and move people rapidly across great distances, time became much more critical and the standardization of time was essential to efficient operation of railroads.

In 1878, Canadian Sir Sanford Fleming proposed the system of Time Around the World zones that we use today. He recommended that the world be divided into twenty-four time zones, each spaced 15 degrees of longitude apart. Since the earth rotates once every 24 hours and there are 360 degrees of longitude, each hour the earth rotates one-twenty-fourth of a circle or 15 degrees of longitude. Sir Fleming's Time Around the World zones were heralded as a brilliant solution to a chaotic problem worldwide. Matt Rosenberg. Time Zones

The Clock Depot - Check for Time Around the World clocks. Order on-line, US shipment. www.theclockdepot.com

Time and Date - Check the time around the World. www.timeanddate.com

The Time Around the World Server - Current time around the world, information, time converter, meeting planner and more. www.worldtimeserver.com

About - Time Zones, an article from Matt Rosenberg about Time Around the World. geography.about.com

WorldtimeŽ - Interactive atlas and time information as well as sunrise and sunset times in several hundred cities worldwide. www.worldtime.com

Time Around the World clock

Coordinated Universal Time

Coordinated Universal Time (UTC) is a high-precision atomic time standard. UTC has uniform seconds defined by International Atomic Time (TAI), with leap seconds announced at irregular intervals to compensate for the earth's slowing rotation and other discrepancies. The leap seconds allow UTC to closely track Universal Time (UT), a time standard based not on the passage of seconds, but the earth's angular rotation. Time Around the World zones are expressed as positive or negative offsets from UTC. As the zero-point reference, UTC is also referred to as Zulu time (Z). UTC is often referred to as Greenwich Mean Time when describing time zones, although strictly speaking, it is only an approximation.