fanf2 / bulletin-a

When will the next leap second happen?

When will the next leap second happen?

the results from this code are discussed in a twitter thread https://twitter.com/fanf/status/1386838657093586944

The IERS publishes a number of bulletins about UTC and leap seconds.

https://www.iers.org/IERS/EN/Publications/Bulletins/bulletins.html

Bulletin C (twice a year) announces whether a leap second will or won't happen.

Bulletin A (weekly, every Thursday) contains detailed predictions of how UT1 (earth rotation angle) will differ from UTC for the next year.

When UT1-UTC grows significantly more than half a second, a leap second is announced to keep them close together.

Historically, UT1-UTC has always decreased, and leap seconds have always been positive. But at the moment, UT1-UTC is increasing. If this continues long enough, there could be a negative leap second.

As well as a table of predictions for the next year, Bulletin A also contains a simple formula that can be used for more long-term projections. We can use this formua to estimate when the next leap second might happen.

It isn't clear to me how far into the future it is sensible to use this formula. The formula changes from week to week, so I thought it would be informative to see how the prediction for the next leap second changes in each issue of Bulletin A.

this program

This repository contains a Rust program that downloads Bulletin A, parses it, and calculates a forecast of when the next leap second might happen.

If you type cargo run you should see output like:

	Finished dev [unoptimized + debuginfo] target(s) in 0.04s
	 Running `target/debug/bulletin-a`
fetching https://datacenter.iers.org/data/6/bulletina-xxxiv-017.txt
2021-04-29 -> 2028-06-30 (-) UT1-UTC +0.514 ± 0.092 s (lod -260 µs)

The first date is the date of the latest Bulletin A.

The second date is when the next leap second might happen. A row of question marks indicates that there is no leap second in the foreseeable future.

The (+) or (-) indicates whether it is predicted to be a positive or negative leap second.

Then follow some numbers showing the forecast difference between UT1 and UTC at the time of the leap second, and the accuracy of the forecast.

Finally is the length-of-day value used by the prediction formula, given as microseconds different from 24 * 60 * 60 seconds. Until recently this number has been positive.

options

• type cargo run 50

  to show forecasts from the last 50 issues of Bulletin A

  by default one is shown

• type cargo run 1 0.75

  to use a threshold of 0.75 seconds when forecasting the next leap second; a leap second is predicted when UT1-UTC grows more than this threshold

  by default the threshold is 0.60 seconds

example output

You can see the transition from days slightly longer to slightly shorter than 24 * 60 * 60 seconds with cargo run -- 100 0.6

2020-09-17 -> 2032-06-30 (+) UT1-UTC -0.470 ± 0.133 s (lod +60 µs)
2020-09-24 -> 2033-06-30 (+) UT1-UTC -0.487 ± 0.141 s (lod +60 µs)
2020-10-01 -> 2034-06-30 (+) UT1-UTC -0.452 ± 0.149 s (lod +50 µs)
2020-10-08 -> 2037-06-30 (+) UT1-UTC -0.441 ± 0.173 s (lod +40 µs)
2020-10-15 -> 2040-06-30 (+) UT1-UTC -0.412 ± 0.195 s (lod +30 µs)
2020-10-22 -> 2045-06-30 (+) UT1-UTC -0.377 ± 0.231 s (lod +20 µs)
2020-10-29 -> 2045-06-30 (+) UT1-UTC -0.376 ± 0.231 s (lod +20 µs)
2020-11-05 -> 2054-06-30 (+) UT1-UTC -0.318 ± 0.292 s (lod +10 µs)
2020-11-12 -> ????-??-?? (?)
2020-11-19 -> ????-??-?? (?)
2020-11-26 -> 2158-12-31 (-) UT1-UTC +0.843 ± 0.841 s (lod -20 µs)
2020-12-03 -> 2073-12-31 (-) UT1-UTC +0.416 ± 0.411 s (lod -30 µs)
2020-12-10 -> 2053-12-31 (-) UT1-UTC +0.317 ± 0.288 s (lod -40 µs)
2020-12-17 -> 2048-12-31 (-) UT1-UTC +0.347 ± 0.255 s (lod -50 µs)
2020-12-24 -> 2042-12-31 (-) UT1-UTC +0.400 ± 0.212 s (lod -70 µs)
2020-12-31 -> 2040-12-31 (-) UT1-UTC +0.422 ± 0.198 s (lod -80 µs)
2021-01-07 -> 2037-12-31 (-) UT1-UTC +0.459 ± 0.175 s (lod -100 µs)
2021-01-14 -> 2035-12-31 (-) UT1-UTC +0.443 ± 0.159 s (lod -110 µs)
2021-01-21 -> 2033-12-31 (-) UT1-UTC +0.458 ± 0.143 s (lod -130 µs)
2021-01-28 -> 2033-12-31 (-) UT1-UTC +0.503 ± 0.142 s (lod -140 µs)
2021-02-04 -> 2031-12-31 (-) UT1-UTC +0.476 ± 0.125 s (lod -160 µs)
2021-02-11 -> 2031-12-31 (-) UT1-UTC +0.511 ± 0.125 s (lod -170 µs)
2021-02-18 -> 2030-12-31 (-) UT1-UTC +0.488 ± 0.116 s (lod -180 µs)
2021-02-25 -> 2030-12-31 (-) UT1-UTC +0.526 ± 0.116 s (lod -190 µs)
2021-03-04 -> 2030-06-30 (-) UT1-UTC +0.502 ± 0.111 s (lod -200 µs)
2021-03-11 -> 2029-12-31 (-) UT1-UTC +0.525 ± 0.107 s (lod -210 µs)
2021-03-18 -> 2029-12-31 (-) UT1-UTC +0.559 ± 0.107 s (lod -220 µs)
2021-03-25 -> 2028-12-31 (-) UT1-UTC +0.509 ± 0.097 s (lod -230 µs)
2021-04-01 -> 2028-12-31 (-) UT1-UTC +0.538 ± 0.097 s (lod -240 µs)
2021-04-08 -> 2028-12-31 (-) UT1-UTC +0.564 ± 0.097 s (lod -250 µs)
2021-04-15 -> 2028-12-31 (-) UT1-UTC +0.561 ± 0.097 s (lod -250 µs)
2021-04-22 -> 2028-06-30 (-) UT1-UTC +0.515 ± 0.092 s (lod -260 µs)
2021-04-29 -> 2028-06-30 (-) UT1-UTC +0.514 ± 0.092 s (lod -260 µs)
2021-05-06 -> 2028-06-30 (-) UT1-UTC +0.512 ± 0.091 s (lod -260 µs)
2021-05-13 -> 2028-12-31 (-) UT1-UTC +0.578 ± 0.096 s (lod -260 µs)
2021-05-20 -> 2028-12-31 (-) UT1-UTC +0.573 ± 0.096 s (lod -260 µs)
2021-05-27 -> 2028-12-31 (-) UT1-UTC +0.569 ± 0.096 s (lod -260 µs)
2021-06-03 -> 2028-12-31 (-) UT1-UTC +0.539 ± 0.095 s (lod -250 µs)
2021-06-10 -> 2028-12-31 (-) UT1-UTC +0.536 ± 0.095 s (lod -250 µs)
2021-06-17 -> 2028-12-31 (-) UT1-UTC +0.534 ± 0.095 s (lod -250 µs)
2021-06-24 -> 2028-12-31 (-) UT1-UTC +0.534 ± 0.095 s (lod -250 µs)
2021-07-01 -> 2028-12-31 (-) UT1-UTC +0.534 ± 0.095 s (lod -250 µs)
2021-07-08 -> 2028-12-31 (-) UT1-UTC +0.531 ± 0.094 s (lod -250 µs)
2021-07-15 -> 2028-12-31 (-) UT1-UTC +0.527 ± 0.094 s (lod -250 µs)
2021-07-22 -> 2028-12-31 (-) UT1-UTC +0.522 ± 0.094 s (lod -250 µs)
2021-07-29 -> 2029-06-30 (-) UT1-UTC +0.509 ± 0.099 s (lod -240 µs)
2021-08-05 -> 2029-06-30 (-) UT1-UTC +0.505 ± 0.098 s (lod -240 µs)
2021-08-12 -> 2029-06-30 (-) UT1-UTC +0.505 ± 0.098 s (lod -240 µs)
2021-08-19 -> 2029-12-31 (-) UT1-UTC +0.546 ± 0.103 s (lod -230 µs)
2021-08-26 -> 2029-12-31 (-) UT1-UTC +0.548 ± 0.103 s (lod -230 µs)
2021-09-02 -> 2029-12-31 (-) UT1-UTC +0.550 ± 0.102 s (lod -230 µs)
2021-09-09 -> 2029-12-31 (-) UT1-UTC +0.551 ± 0.102 s (lod -230 µs)
2021-09-16 -> 2029-12-31 (-) UT1-UTC +0.554 ± 0.102 s (lod -230 µs)
2021-09-23 -> 2029-12-31 (-) UT1-UTC +0.556 ± 0.102 s (lod -230 µs)
2021-09-30 -> 2029-12-31 (-) UT1-UTC +0.558 ± 0.102 s (lod -230 µs)
2021-10-07 -> 2029-12-31 (-) UT1-UTC +0.560 ± 0.102 s (lod -230 µs)
2021-10-14 -> 2029-12-31 (-) UT1-UTC +0.532 ± 0.101 s (lod -220 µs)
2021-10-21 -> 2029-12-31 (-) UT1-UTC +0.533 ± 0.101 s (lod -220 µs)
2021-10-28 -> 2029-12-31 (-) UT1-UTC +0.534 ± 0.101 s (lod -220 µs)
2021-11-04 -> 2029-12-31 (-) UT1-UTC +0.535 ± 0.101 s (lod -220 µs)
2021-11-11 -> 2029-12-31 (-) UT1-UTC +0.507 ± 0.101 s (lod -210 µs)
2021-11-18 -> 2029-12-31 (-) UT1-UTC +0.509 ± 0.100 s (lod -210 µs)
2021-11-25 -> 2029-12-31 (-) UT1-UTC +0.510 ± 0.100 s (lod -210 µs)
2021-12-02 -> 2029-12-31 (-) UT1-UTC +0.510 ± 0.100 s (lod -210 µs)
2021-12-09 -> 2029-12-31 (-) UT1-UTC +0.507 ± 0.100 s (lod -210 µs)
2021-12-16 -> 2029-12-31 (-) UT1-UTC +0.503 ± 0.100 s (lod -210 µs)
2021-12-23 -> 2030-12-31 (-) UT1-UTC +0.545 ± 0.109 s (lod -200 µs)
2021-12-30 -> 2030-12-31 (-) UT1-UTC +0.542 ± 0.109 s (lod -200 µs)
2022-01-06 -> 2030-12-31 (-) UT1-UTC +0.539 ± 0.108 s (lod -200 µs)
2022-01-13 -> 2030-12-31 (-) UT1-UTC +0.538 ± 0.108 s (lod -200 µs)
2022-01-20 -> 2030-12-31 (-) UT1-UTC +0.539 ± 0.108 s (lod -200 µs)
2022-01-27 -> 2030-12-31 (-) UT1-UTC +0.542 ± 0.108 s (lod -200 µs)
2022-02-03 -> 2030-12-31 (-) UT1-UTC +0.546 ± 0.108 s (lod -200 µs)
2022-02-10 -> 2030-12-31 (-) UT1-UTC +0.548 ± 0.108 s (lod -200 µs)
2022-02-17 -> 2029-12-31 (-) UT1-UTC +0.508 ± 0.098 s (lod -210 µs)
2022-02-24 -> 2029-12-31 (-) UT1-UTC +0.509 ± 0.098 s (lod -210 µs)
2022-03-03 -> 2029-12-31 (-) UT1-UTC +0.515 ± 0.098 s (lod -210 µs)
2022-03-10 -> 2029-12-31 (-) UT1-UTC +0.549 ± 0.098 s (lod -220 µs)
2022-03-17 -> 2029-06-30 (-) UT1-UTC +0.516 ± 0.093 s (lod -230 µs)
2022-03-24 -> 2029-06-30 (-) UT1-UTC +0.521 ± 0.092 s (lod -230 µs)
2022-03-31 -> 2028-12-31 (-) UT1-UTC +0.533 ± 0.088 s (lod -240 µs)
2022-04-07 -> 2028-12-31 (-) UT1-UTC +0.561 ± 0.087 s (lod -250 µs)
2022-04-14 -> 2028-12-31 (-) UT1-UTC +0.587 ± 0.087 s (lod -260 µs)
2022-04-21 -> 2028-12-31 (-) UT1-UTC +0.590 ± 0.087 s (lod -260 µs)
2022-04-28 -> 2028-06-30 (-) UT1-UTC +0.540 ± 0.082 s (lod -270 µs)
2022-05-05 -> 2027-12-31 (-) UT1-UTC +0.533 ± 0.077 s (lod -280 µs)
2022-05-12 -> 2027-12-31 (-) UT1-UTC +0.528 ± 0.076 s (lod -280 µs)
2022-05-19 -> 2028-06-30 (-) UT1-UTC +0.549 ± 0.081 s (lod -280 µs)
2022-05-26 -> 2027-12-31 (-) UT1-UTC +0.541 ± 0.076 s (lod -290 µs)
2022-06-02 -> 2027-12-31 (-) UT1-UTC +0.542 ± 0.076 s (lod -290 µs)
2022-06-09 -> 2027-12-31 (-) UT1-UTC +0.562 ± 0.076 s (lod -300 µs)
2022-06-16 -> 2027-12-31 (-) UT1-UTC +0.562 ± 0.075 s (lod -300 µs)
2022-06-23 -> 2027-12-31 (-) UT1-UTC +0.564 ± 0.075 s (lod -300 µs)
2022-06-30 -> 2027-12-31 (-) UT1-UTC +0.580 ± 0.075 s (lod -310 µs)
2022-07-07 -> 2027-12-31 (-) UT1-UTC +0.598 ± 0.075 s (lod -320 µs)
2022-07-14 -> 2027-12-31 (-) UT1-UTC +0.596 ± 0.075 s (lod -320 µs)
2022-07-21 -> 2027-12-31 (-) UT1-UTC +0.612 ± 0.074 s (lod -330 µs)
2022-07-28 -> 2027-12-31 (-) UT1-UTC +0.608 ± 0.074 s (lod -330 µs)
2022-08-04 -> 2027-12-31 (-) UT1-UTC +0.605 ± 0.074 s (lod -330 µs)
2022-08-11 -> 2027-06-30 (-) UT1-UTC +0.535 ± 0.069 s (lod -340 µs)

licence

This code was written by Tony Finch <[e-mail]>
You may do anything with this. It has no warranty.
https://creativecommons.org/publicdomain/zero/1.0/
SPDX-License-Identifier: CC0-1.0