World Clock Webservice?

Question

What is the most reliable World Clock Webservice that you use?

Answer 1

Understood about latency. With that in mind, I go to NIST's site for US times and World Time Server for the rest. Don't know if either is the "best".

Answer 2

I think due to latency, there is no such thing as a reliable atomic clock webservice.

Answer 3

A NTP webservice would be fine as long as the latency is predictable. NTP is a wire protocol and very lightweight to remove any moving pieces that may cause additional variation in latency (aka jitter). A SOAP stack would introduce more variability.

Answer 4

Here's a blog post which comes to the same conclusion.

Purists are quick to point to the accuracy problem. But I bet you could not even get perfectly accurate time even if your application was sitting on the same server as the atomic clock software itself.

I think there is a need for a clock Web Service. I can think of a few scenarios where it doesn't matter being off a few seconds.

Aside accuracy, another challenging area of serving up date and time is taking into account the daylight saving details of most country. That is something even the latest OSes struggle to get right. But that is definitely something that would make a clock Web Service valuable.

Answer 5

Unfortunately, you'll probably never get a really accurate atomic clock webservice due to latency issues with the transport of the messages/packets back and forth from your machine to the server.

Most atomic clocks that are accessible over the internet use a specific protocol called the Network Time Protocol that includes a jitter buffer which specifically accounts for and adjusts based upon the latency of the transport. This provides a more accurate representation of the atomic clock's time than using a web-service over HTTP.

I think if you must use a webservice, the most accurate one will be the one hosted on a server that is physically and geographically closest to you and also has the least number of network hops to get from your own machine to the server, since this will reduce the latency of the packets.

Answer 6

Since there are so few web services out there delivering time, http://www.timeapi.org/utc/now is only reliable web service that I know of (besides http://www.earthtools.org/timezone/0/0, which does not appear to be reliable). Therefore it's the most accurate one I can recommend, especially if you are just using it for determining the difference between local time and UTC time, which can be rounded to the nearest 15 minutes. And if you want the time in a specific time zone, replace utc with the three-letter abbreviation for the time zone -- i.e., http://www.timeapi.org/est/now for the Eastern Standard Time.