Should the leap second be eliminated?
1–10 of 25 posts
Re: Should the leap second be eliminated?
#2For a backgrounder, read this CACM article:
http://cacm.acm.org/magazines/2011/5/107699-the-one-second-w...
I've wondered, would the technical problems described be ameliorated if a longer timeframe was given? At the moment, we have about six months notice of leap seconds; what if we lengthened this to, say, two years?
That said, I'm not really sympathetic to the proposal. We already have the highly predictable International Atomic Time (TAI); why if we want this predictability, not just use TAI instead of trying to change UTC?
Re: Should the leap second be eliminated?
#3>Over decades, the difference between Earth-based time and atomic clock time would amount to a few minutes, but over 500 years, they would be out by an hour. Over millennia, the discrepancy would grow even more.
Is this really true? Based on http://en.wikipedia.org/wiki/Leap_second
It seems like there's only been 25 leap seconds in 40 years. That's around a minute every century..
Re: Should the leap second be eliminated?
#4>Over decades, the difference between Earth-based time and atomic clock time would amount to a few minutes, but over 500 years, they would be out by an hour. Over millennia, the discrepancy would grow even more. Is this really true? Based on http://en.wikipedia.org/wiki/Leap_second It seems like there's only been 25 leap seconds in 40 years. That's around a minute every century..
Leap seconds are expected to become more frequent, and the last decade has had unusually few leap seconds.
Re: Should the leap second be eliminated?
#5>Over decades, the difference between Earth-based time and atomic clock time would amount to a few minutes, but over 500 years, they would be out by an hour. Over millennia, the discrepancy would grow even more. Is this really true? Based on http://en.wikipedia.org/wiki/Leap_second It seems like there's only been 25 leap seconds in 40 years. That's around a minute every century..
Leap seconds are expected to become more frequent, and the last decade has had unusually few leap seconds.
Does that mean we expect there to be more than a couple of leap seconds every year? (Based on the "more than an hour over 500 years" statement)
Re: Should the leap second be eliminated?
#6I like the leap-hour once every 500 years or so idea.
But I suspect in practice, it would never be actually assessed. When it comes due, everyone alive would be more accustomed to the 'hour off' times than the 500-years-ago time, so natural tendencies to eschew change in such matters would make following-through on the promised leap-hour unlikely.
Re: Should the leap second be eliminated?
#7Earlier quoted context omitted.
Leap seconds are expected to become more frequent, and the last decade has had unusually few leap seconds.
Does that mean we expect there to be more than a couple of leap seconds every year? (Based on the "more than an hour over 500 years" statement)
Err, yes, that does sound an order of magnitude out, now I come to think of it.
The original proposal allows updates four times a year, though only the July and December updates have been used.
Re: Should the leap second be eliminated?
#8Why don't we let GPS satellites and NTP broadcast both "regular time" and International Atomic Time (TAI), and let each user use the one that fits best?
So: satellite navigation, financial services and flight control systems use TAI, everybody else uses regular time?
To make the difference obvious and prevent misunderstandings, TAI could even have a different form, like a pure integer of "seconds after date X". So nobody except programmers for financial services and other specialized systems would ever get to see TAI, and everybody's happy?
Re: Should the leap second be eliminated?
#9Earlier quoted context omitted.
Does that mean we expect there to be more than a couple of leap seconds every year? (Based on the "more than an hour over 500 years" statement)
Err, yes, that does sound an order of magnitude out, now I come to think of it. The original proposal allows updates four times a year, though only the July and December updates have been used.
Four times a year, with up to two seconds added each time should put an upper bound for adjustments accumulated over 500 years to:
500 years * 4 updates/year * 2 seconds/update = 4000 seconds = 66 2/3 minutes
So an hour in 500 years seems to require adjusting almost as much as we can, which isn't realistic.
Re: Should the leap second be eliminated?
#10Why don't we let GPS satellites and NTP broadcast both "regular time" and International Atomic Time (TAI), and let each user use the one that fits best? So: satellite navigation, financial services and flight control systems use TAI, everybody else uses regular time? To make the difference obvious and prevent misunderstandings, TAI could even have a different form, like a pure integer of "seconds after date X". So no…
I think you're on the right track, but I'd take it a step further: Whenever you're displaying what the time is to a human being, convert to UTC. In all other cases - especially storage and transmission etc. - use TAI.
We have very rich libraries for dealing with time in software, so it's not like it would be a huge drag.
There are still some unaddressed edge cases, of course. Say there's a leap second on 1 July. Now consider the interval 14:00 30 June - 14:00 1 July. In "human time" it's 24 hours, but in computer time it's 24h00m01s - and, conversely and perhaps more dangerous, should "14:00 30 June" + 24 hours come out as 13:59:59 or 14:00:00?