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

bzzzzt

[epine]

TFA:

the newest of which is so accurate, it gains or loses only a second every 300 million years

First of all, that's aspirational (or was) in most of the other articles I found.

Contra TFA: NIST Launches NIST-F2

Primary standards such as NIST-F1 and NIST-F2 are operated for periods of a few weeks several times each year to calibrate NIST timescales, collections of stable commercial clocks such as hydrogen masers used to keep time ... Technically, both F1 and F2 are frequency standards, meaning they are used to measure the size of the SI second and calibrate the "ticks" of other clocks.

Unfortunately, even contra TFA is weak geek tea:

Both NIST-F1 and NIST-F2 measure the frequency of a particular transition in the cesium atom—which is 9,192,631,770 vibrations per second, and is used to define the second, the international (SI) unit of time.

I guess there's a reason why people with tiny UIDs memorize pi to a silly number of places: it helps you not leave off the other five or six significant digits in the rare case where it actually matters. The real frequency standard is only, like, approximately a million times better than that long-assed, dock-tailed string of digits visually implies.

Truly inconceivable—almost—and yet barely able to time slice the total perspective vortex.

Finally, some obligatory geek porn: Atomic fountain

Re:Nut in charge of the nut house.

[amorsen]

Unfortunately, Unix and NTP treat leap seconds completely different from Daylight Saving. They actually mess with the real measured clock, slowing it down. This is just completely broken of course, suddenly seconds aren't one second long any more. This has lead to system crashes and all sorts of fun.

There are two solutions to this: Either the NTP guys get their heads out of their asses, or leap seconds are abolished.

Unix is mostly ready, there can be 62 seconds in a minute in C, so all you do is switch the timezone files to the "right" directory instead of the "posix" directory (on GNU systems at least). But that cannot be done until NTP works.

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

Re:Horrible mostly wrong article title

[Ungrounded Lightning]

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.

I knew Dr. Dave when he was still at the University of Michigan, doing the Data Concentrator and the Language Lab's automation, and I was in high school and hanging around the campus.

Great guy.