Tom Van Baak tvb at LeapSecond.com
Thu Mar 12 03:45:29 EDT 2015


> And UTC has failed miserably.  POSIX says UTC has no leaps.
> Google says UTC has occasional days with stretches of seconds which
> are of varying lengths.  De facto, there is no single UTC time scale.

Right! And many more examples of UTC fails -- the RTC of any unix computer. Any windows computer. Arduino and the microcontroller world. GPS receivers displaying 59 twice or 00 twice. IRIG. FAT (memory cards). Excel. eBay. Analog clocks.

It's getting increasingly awkward decade after decade to have all these holes in the practical implementation of UTC. Remember the paper that started all of this had "time to change" in the title:

Remember also that in the 60's when leap seconds were conceived there were no personal computers, no quartz wrist watches, no internet, sailors used sextants or LORAN, WWV ticked on short-wave, teletypes were 110 baud, NASA used nixie tubes (no LED's), phones were black and rotary, you could dial in town with 4 digits, TV's had 3 channels, computers were the size of rooms and turned off at night, etc. Almost nobody knew about or was affected by leap seconds.

It was a reasonable technical solution for the era. I think those that want to get rid of leap seconds have a point; it is too awkward a universal solution for the 21st century.

> But the bottom line for engineers who are implementing operational
> systems that depend on timing is much simpler.
> If you want to engage with a 15 year long international flame war
> where people cannot agree on elapsed time to within several seconds,
> then go ahead, choose the internationally-recommended UTC.
> But if you want to get something working that does not get bothered by
> differences of several nanoseconds, then ignore the international
> recommendations and choose GPS time, Galileo, BeiDou, the Indian
> satellite system time, or some PTP-based system via a device which
> claims to be using one of those to supply TAI.

Good point. I agree. But its sad. And would have been unnecessary. This proliferation of timescales, even back in the late 90's, is the main reason (so I was told) that USNO proposed that leap seconds be re-considered. Dennis can provide more info if he's still on the list.


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