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Leap second hiatus

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Re: Leap second hiatus

#81

Post by Unklejoe »

dgrin91 wrote: post #18
labster wrote: post #15

Can we take a longer hiatus on leap seconds, maybe 79 years or so, and only update once a century? Local apparent noon being off by 30 seconds or so has approximately zero impact on my daily life, but stupid things in datetime libraries do occasionally have impact. If we can’t throw off the oppression of UTC and greet TAI as liberators, at least adjust the clock at regular, very infrequent dates.

Pretty sure there are lots of things that you use everyday that actually require precision time, such as GPS.

GPS time is already immune from leap seconds. It has a fixed offset from TAI of 19 seconds and always will.

It also contains UTC offset information so that you can derive the current UTC time from GPS if you wanted to.

Re: Leap second hiatus

#82

Post by PaulAJ »

dflock wrote: post #16

What causes changes in the rate of rotation of the earth?

Good question. It means that something is moving mass away from the axis of the Earth.

There are only two candidates I can think of:

1. Movements in magma below the Earth's crust.

2. Global warming. Less ice at the poles means that water has moved away from the Earth's axis, which will slow the rotation down. I haven't run the maths to see if that adds up though.

Re: Leap second hiatus

#83

Post by dfox »

zokier wrote: post #80
bloak wrote: post #58

Earlier quoted context omitted.

People who can't cope with leap seconds should stop pestering the people who define UTC and just switch to TAI. They can do that now. No one is stopping them. Leap seconds are a pain and I myself would happily choose TAI over UTC for the system clock on a typical embedded system. However, for civil time keeping and for some technical purposes, UTC as currently defined is exactly what we need. Don't fuck with it.

> However, for civil time keeping and for some technical purposes, UTC as currently defined is exactly what we need. Don't fuck with it. You are asserting that without any justification. I see no benefits and lots of downsides in having leap seconds in civil time specifically.

I think that the point is that for most definitions of "civil timekeeping" you just do what Unix does and ignore the leap seconds altogether and simply live with the fact that once in a while one wall-clock second takes two SI seconds (or does not exist at all), probably by simply being completely oblivious to that fact.

Re: Leap second hiatus

#84

Post by macintux »

mdpm wrote: post #35

Re: the 'negative second' fears - in usual operation, NTP adjusts your local machine downward all the ... time. There's really nothing to be afraid of; a few services would implement some skew, the rest of us would get NTP updates and life continues.

ntpd can be configured to disallow negative time adjustments, and anything that runs a database definitely should have that configured. The system clock is presumed to always increment for most databases, and screwing with that can cause data loss.

Re: Leap second hiatus

#85

Post by zokier »

dfox wrote: post #83
zokier wrote: post #80

Earlier quoted context omitted.

> However, for civil time keeping and for some technical purposes, UTC as currently defined is exactly what we need. Don't fuck with it. You are asserting that without any justification. I see no benefits and lots of downsides in having leap seconds in civil time specifically.

I think that the point is that for most definitions of "civil timekeeping" you just do what Unix does and ignore the leap seconds altogether and simply live with the fact that once in a while one wall-clock second takes two SI seconds (or does not exist at all), probably by simply being completely oblivious to that fact.

Don't even get me started on UNIX time. On that I agree with the parent comment, whatever the time scale, you shouldn't fuck with it. Alas, UNIX is what it is..

Re: Leap second hiatus

#86

Post by ballenf »

japanuspus wrote: post #38
dflock wrote: post #16

What causes changes in the rate of rotation of the earth?

The angular momentum of the "earth system" is constant [1]. The variation in angular velocity of the solid earth can be ascribed to change in the angular momentum carried by oceans and atmosphere. These changes can be due to change in velocity (winds, currents) or moment of inertia (moisture in atmosphere). [1] If we ignore friction due to tidal forces from moon and sun (which is valid on these time-scales), the "ear…

Is the total mass of all mined minerals and hydrocarbons more than rounding error in the calculation of moment of inertia?

This would assume that mined materials stay at a higher elevation than they were. And that the materials above those items didn't collapse down and/or aren't heavier than the mined mass.

Re: Leap second hiatus

#87

Post by sarah180 »

labster wrote: post #15

Can we take a longer hiatus on leap seconds, maybe 79 years or so, and only update once a century? Local apparent noon being off by 30 seconds or so has approximately zero impact on my daily life, but stupid things in datetime libraries do occasionally have impact. If we can’t throw off the oppression of UTC and greet TAI as liberators, at least adjust the clock at regular, very infrequent dates.

Can we take this solved problem and replace it with a new one that has details we haven't figured out?

Re: Leap second hiatus

#88

Post by beagle3 »

lifthrasiir wrote: post #44
beagle3 wrote: post #41

Earlier quoted context omitted.

> The fact that any non-UI code uses any time standard except TAI is a very unfortunate historical mistake that will hopefully be cleaned up over the next few years. Unfortunately, almost everything is UI code in some way, so this won't be cleaned up. The problem with TAI is that you cannot convert a future time to UTC if it is farther than 6 months or so in the future (because leap seconds have not been decided), so…

> The problem with TAI is that you cannot convert a future time to UTC if it is farther than 6 months or so in the future [...] Centimeter's argument is that such time should not be converted to TAI in advance, much like the local time for the future point (since the local time zone offset may change). All points on this also apply to the local time, e.g. it's already true that non-updatable embedded systems can't re…

They can’t do local time, but they can do UTC (and do it) without much investment if you run an NTP client. (Have 500 or so such units deployed, SNTP was giving too much trouble, switched to chrony at some point and those units require much less support)

Re: Leap second hiatus

#89

Post by forgotmypw17 »

labster wrote: post #15

Can we take a longer hiatus on leap seconds, maybe 79 years or so, and only update once a century? Local apparent noon being off by 30 seconds or so has approximately zero impact on my daily life, but stupid things in datetime libraries do occasionally have impact. If we can’t throw off the oppression of UTC and greet TAI as liberators, at least adjust the clock at regular, very infrequent dates.

How does TAI relate to Epoch time?

More and more I use Epoch time for most things just because of how convenient it is.

I rarely need sub-second granularity, and it's just one number, so it's sortable, math-able, etc.

Then whoever is doing the display can convert it any way they want to.

Re: Leap second hiatus

#90

Post by forgotmypw17 »

> At the moment the Earth is rotating faster than in recent decades: these shorter days, with a lower length-of-day, means the milliseconds accumulate more slowly, and we get fewer leap seconds.

Does anyone know why Earth's rotation has sped up?

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