2016 seems long to me (Leap second)

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In summary: The decision to add a leap second has been debated for years, but it was finally approved by the International Telecommunication Union in 2015. Some people worry that the extra second will add up over time, causing our calendar to run a few days off.In summary, we are getting a leap second! 2016 really is too long.
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jim mcnamara
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Now I know why: http://phys.org/news/2016-12-extra_1.html
We are getting a leap second! 2016 really is too long. :cry: If you are an astronomer or programmer you know about these corrections to NIST atomic clock time (UTC). The Earth's period of rotation is not constant over long periods. Very slightly, Earth slowing down.

Programming:
The POSIX standards (for UNIX) do not require tracking leap seconds. But some OS developers have decided to keep track of them - Linux for example. GPS does not deal with them.

Here is a discussion:
https://www.wired.com/2015/01/torvalds_leapsecond/
 
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:nb):nb):nb):nb):nb):nb)
 
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jim mcnamara said:
GPS does not deal with them.
Interesting, I would have assumed one second would be fairly crucial, I thought GPS even took time dilation into account. Am I missing something here. ?
 
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Oops - the second will be added to 2017, my apologies.

NIST source file for programming - leap seconds: https://github.com/eggert/tz/blob/master/leap-seconds.list

@1oldman2 - yes, gps does care about relativity. GPS depends solely on the duration (delay) of the signal until reception time. So all that matters in terms of elapsed time is that: Every satellite is on the same time precisely, and the ephemeris portrays the exact sub-satellite point Then corrections like WASD, are applied to correct for atmospheric refraction. GPS uses its own time standard, which can be converted to UTC.

There is a LOT to this that I blithely ignored. Links:
Math: http://www.maa.org/sites/default/files/pdf/cms_upload/Thompson07734.pdf
Overview: http://www.oc.nps.edu/oc2902w/gps/timsys.html
 
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jim mcnamara said:
@1oldman2 - yes, gps does care about relativity. GPS depends solely on the duration (delay) of the signal until reception time. So all that matters in terms of elapsed time is that: Every satellite is on the same time precisely, and the ephemeris portrays the exact sub-satellite point Then corrections like WASD, are applied to correct for atmospheric refraction. GPS uses its own time standard, which can be converted to UTC.
Thanks, sometimes this entire site could be titled "T.I.L." :smile:
 
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https://www.nasa.gov/feature/goddar...ng-nasas-sdo-adds-leap-second-to-master-clock
On Dec. 31, 2016, official clocks around the world will add a leap second just before midnight Coordinated Universal Time - which corresponds to 6:59:59 p.m. EST. NASA missions will also have to make the switch, including the Solar Dynamics Observatory, or SDO, which watches the sun 24/7.

Clocks do this to keep in sync with Earth's rotation, which gradually slows down over time. When the dinosaurs roamed Earth, for example, our globe took only 23 hours to make a complete rotation. In space, millisecond accuracy is crucial to understanding how satellites orbit.
 

Related to 2016 seems long to me (Leap second)

1. What is a leap second?

A leap second is a one-second adjustment that is occasionally applied to Coordinated Universal Time (UTC) to keep it in line with the Earth's rotation. This ensures that astronomical time and atomic time remain in sync.

2. What causes a leap second?

The Earth's rotation is gradually slowing down due to tidal forces caused by the moon. This means that the length of a day is slowly increasing. To account for this, a leap second is added to UTC every few years.

3. When was the last leap second added?

The last leap second was added on December 31, 2016 at 23:59:60 UTC. This means that the clock went from 23:59:59 to 23:59:60 before ticking over to 00:00:00 on January 1, 2017 in most time zones.

4. How often are leap seconds added?

Leap seconds are added irregularly, typically occurring every 1-3 years. The decision to add a leap second is made by the International Earth Rotation and Reference Systems Service (IERS), based on the Earth's rotation and other factors.

5. Do all countries observe leap seconds?

Most countries follow UTC and therefore observe leap seconds, but some countries and organizations choose not to. For example, China and India do not use leap seconds, and some computer systems do not account for them properly, which can lead to technical issues.

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