Meet the Guy Whose Software Keeps the World's Digital Clocks In Sync (ieee.org)

New submitter Wave723 quotes a story on IEEE: In many cases, the internal clock that ticks away in a laptop or desktop computer is synchronized to an official time service maintained by the U.S. National Institute of Standards and Technology (NIST). This free service shares Coordinated Universal Time with personal devices, web browsers, financial trading software and e-mail programs throughout the world. The service receives 150,000 requests per second (roughly 16 billion a day) from systems that repeatedly ask, 'What time is it?' "If you have a PC, it's probably synchronized to the time service," says Judah Levine, the man who originally built servers and programmed software to send time over the Internet for NIST back in 1993.

Comments

Re:Nut in charge of the nut house.

[tlhIngan]

Because the leap second like DST are _artificial_ and adds unnecessary complexity to an otherwise brain-dead simple algorithm. Complexity == Bugs.

The only one who gives a fuck about leap seconds are scientists.

Stop over-engineering a simple concept. Time should be monotonic, and consistent. Not this one-off shenanigans.

The problem is there is a lot of time.

You may remember GMT, nowadays known as UT (not to be confused with UTC). GMT is time based on the Earth's rotation - when the sun is directly overhead, it's noon. There are approximately 86,400 seconds in a day here, but the mean solar day varies because Earth's rotation is not uniform. UT1 is the most common form of this, which is what time is measured at the prime meridian.

UTC is time derived from the atomic clock. It closely approximates UT, but since Earth's rotation is erratic, to keep the UTC day closely aligned with the UT day, leap seconds are sometimes added to ensure the difference between the two times is under 0.9 seconds.

TAI is the time as told by atomic clocks. Here, a day is exactly 86,400 seconds and there is no such thing as leap seconds - this is purely a monotonic clock that ticks away.

The problem is, well, there are a lot of variables. UT is measured generally once a day and clocks set to its time. UTC is a close approximation and generally used as it's easier to obtain without having to have someone observe the Sun every day to calculate when noon is. TAI is just the atomic clock time.

Leap seconds are introduced to keep UTC and UT relatively close to each other. TAI is allowed to drift, and eventually you'll have noon at midnight.

Which you pick is up to your needs. Leap years were created so people in the Northern hemisphere wouldn't be celebrating summer in December as the calendar drifts away from Earth's position in its orbit..

Then there's TAI, which is the true atomic time

Horrible mostly wrong article title

[Anonymous Coward]

Judah Levine, the gentleman mentioned in the article, built interfaces to existing atomic clocks that allowed other clocks to synchronize with them, which is a worthy achievement.

But today, the vast majority of synchronized clocks are being kept synced by NTP across the Internet, not by radio signals. And although Levine also implemented NTP interfaces at NIST, he didn't invent NTP nor was he responsible for its dominance of Internet timekeeping.

The man who invented NTP and originally wrote the implementation was David L. Mills of the University of Delaware.

Mills is also the man who created the Fuzzballs and EGP, making global-scale internetworking possible.