Good time for all with NIST widget
Time.gov upgrade to Flash lets developers embed accurate time on their sites
- By William Jackson
- Jan 18, 2011
The National Institute of Standards and Technology has released a free widget that lets Web developers embed accurate clocks in their sites.
Once installed on a site, the Adobe Flash applet downloads the digital clock as a Flash object for display in the page in the viewer’s browser. It checks for the viewer’s time zone, then contacts the NIST time server and returns a time stamp to start the clock running. It synchronizes with the time server every 10 minutes.
The widget is the result of public feedback and is the first step toward a general upgrade of the www.time.gov website, which provides accurate time for visitors, said Andrew Novick, a NIST engineer who runs the popular page.
“The current Time.gov works with a Java applet,” Novick said. But Java does not always get along well with Windows. “The problem with Java is every now and then it just fails for some reason,” and must be downloaded again to correct the problem. It also does not have the market penetration of Flash. So the new page will use Flash, and the widget is a preview of some of the new features that the page will have.
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The widget, which is available at no charge, has not yet been widely publicized by NIST but is providing about 100,000 synchronizations a day, Novick said. “It’s grown pretty quickly.”
NIST is the nation’s official civilian timekeeper (the U.S. Naval Observatory keeps time for the military) and contributes to the international Coordinated Universal Time. The NIST Time and Frequency Division in the Boulder, Colo., laboratory is home to the most accurate atomic clock in the world, which uses transitions in Cesium 133 atoms to measure time to within one second every 100 million years.
NIST operates time servers that provide accurate time stamps to a variety of users, including many operating systems that use them to periodically check the accuracy of PC clocks.
The Java clock at time.gov and the Flash clock in the widget only count the time off in seconds, using the PC’s clock for this after the time stamp has been received. Both measure network delay between the user’s browser and the time server to estimate the accuracy of the displayed time, usually within tenths of a second, which is close enough for the average PC, Novick said.
“Computer clocks are pretty poor,” he said. “They can lose several seconds each day. But in 10 minutes,” the time between widget refreshes, “they aren’t going to lose much.”
If inaccuracies are noted when the PC clock display is updated, some operating systems can “steer” the computer’s oscillator that runs the clock to keep it more accurate.
The Time.gov website is run as a public convenience and is not the primary job of the Time and Frequency Division. Novick is not working full time on the page update, so he has no schedule for completing the job.
“If I wanted to make it just the same,” except for using Flash, “it would be simple,” he said. But he intends to make the new page more interactive, with more options and more accurate maps for determining time zones.
The current Time.gov clock is a 24-hour clock, displaying what is usually called military time: Hours after noon continue to increase rather than repeat the previous 12 hours, so that 1 p.m. is 13:00 hours, 2 p.m. is 14:00 hours, and so on. Time on the widget clock can be displayed either in a 12- or 24-hour format, and defaults to 12-hour. This will be incorporated into the new Time.gov. And the “accurate within” label will be changed to “network delay,” which is the time required for the round trip between the user’s computer and time server. Because the time stamp used for the clock only makes a one-way trip, the actual accuracy of the display usually is less than half of the network delay.
But the biggest change will be how time zones are handled, Novick said. The current clock only allows users to choose among U.S. time zones, and rules for time zone borders and observation of Daylight Saving Time are programmed in.
This is not a big deal for the United States, where these changes occur infrequently. But the updated page will use a World Time Database hosted by worldtimeserver.com that continuously updates the frequent changes in the rest of the world’s time zones, including observations of standard and special times. Incorporating the database will enable the site to deliver accurate time throughout the world’s 24 time zones.
“It’s quite the undertaking for us,” Novick said of the upgrade.