One second is currently correctly defined as "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between two hyper-fine levels of the ground state of the caesium-133 atom."
What is UTC?
In 1970 the Coordinated Universal Time system was devised by an international advisory group of technical experts within the International Telecommunication Union (ITU). The ITU felt it was best to designate a single abbreviation for use in all languages in order to minimize confusion. Since unanimous agreement could not be achieved on using either the English word order, CUT, or the French word order, TUC, the acronym UTC was chosen as a compromise. Greenwich Mean Time (GMT) is a 24 hour astronomical time system based on the local time at Greenwich, England. GMT can be considered equivalent to Coordinated Universal Time (UTC) when fractions of a second are not important. However, by international agreement, the term UTC is recommended for all general timekeeping applications, and use of the term GMT is discouraged.
Why won´t WorldTime sync?
Many people asking about Sync difficulties with WorldTime. There are several things that can contribute to difficulties synching using WorldTime:
SimpleTime Protocol:
WorldTime 5 uses the simpletime protocol for synching the clock. This protocol is not permitted by all of the public time servers and this may contribute to failed attempts. Version 6 uses a fully NTP compliant synch process that will eliminate this issue.
Public Servers Busy:
WorldTime synchs to public time servers, with increases traffic on these servers the response time is sometimes too slow and causes WorldTime´s synch module to time-out.
DNS query takes too long:
Some ISPs DNS servers are overloaded and can cause the time it takes to resolve an internet address like time.nist.gov into it´s IP address 192.43.244.18 to take too long and cause WorldTime´s synch module to time-out. This problem can easily be fixed by changing the WorldTime Time Server preference to use the IP address of the time server rather then the address of the server.
Why is WorldTime free?
WorldTime is free because I want it to be! I started writing it because I didn´t want to pay the (sometimes outragious) prices for other world clock software that was available at the time. Now that I have got a viable application I see no reason to charge others for it. Regardless, WorldTime does benifit me in several ways: I learn better programming, I meet tons of interesting people via email, and my web page is completely paid for by the advertizing revenue WorldTime generates. Last but not least... when I started out on the internet using NCSA Moasic as a browser (Netscape didn´t even exist yet!) everything was free - that was the whole point. Now, in my small way, I´m attempting to preserve the origional goald of the internet - free, easy, mutual colloboration and development.
Why are some "major" locations not in the list?
The WorldTime location list is primairly created from user sumbissions via the AddLocation form on the WorldTime web site. I don´t have time to search through data and find all the information but rely on the many users of WorldTime to help out in this area. Thus, if a location is ´missing´ it just means that no one else has submitted it yet and that since you need it it may be high time for someone (hint hint) to do so.