Earth · rotation
The dancing pole
The rotation axis does not always pierce the Earth at the same point: it traces a spiral a few metres wide, the sum of the Chandler wobble (≈ 433 days) and an annual wobble. Ten years of daily measurements, time going up.
- Date
- —
- x
- —
- y
- —
Latest day · excess length of day (C04)
0.159 ms
Chandler period (days)
433
Typical amplitude
≈ 3 to 9 m
IERS Bulletin A daily Earth orientation (USNO finals2000A.all) · U.S. Government work, public domain; cite IERS Bulletin A · 10/23/26
Pole x, y coordinates (USNO Bulletin A), centred on their mean; 1″ ≈ 30.9 m at the surface.
Latest day · excess length of day (C04)
0.159 ms
2025-05-05
IERS EOP 20 C04 daily Earth orientation since 1962 · IERS data, free use with citation (Bizouard et al., 2019) · 10/23/26
Latest UT1 − UTC (Bulletin A)
-0.2081 ± 0.0254 s
2027-10-29
one-second jumps are leap seconds
IERS Bulletin A daily Earth orientation (USNO finals2000A.all) · U.S. Government work, public domain; cite IERS Bulletin A · 10/23/26
Longest day of the C04 series
4.355 ms
1972-04-12
IERS EOP 20 C04 daily Earth orientation since 1962 · IERS data, free use with citation (Bizouard et al., 2019) · 10/23/26
Shortest day of the C04 series
-1.651 ms
2024-07-05
IERS EOP 20 C04 daily Earth orientation since 1962 · IERS data, free use with citation (Bizouard et al., 2019) · 10/23/26
Excess length of day since 1962, yearly mean
IERS EOP 20 C04 daily Earth orientation since 1962 · IERS data, free use with citation (Bizouard et al., 2019) · 10/23/26
Show the data as a table
Excess length of day since 2000, monthly mean
IERS EOP 20 C04 daily Earth orientation since 1962 · IERS data, free use with citation (Bizouard et al., 2019) · 10/23/26
Show the data as a table
UT1 − UTC, last six years
IERS Bulletin A daily Earth orientation (USNO finals2000A.all) · U.S. Government work, public domain; cite IERS Bulletin A · 10/23/26
Show the data as a table
Polar motion, x and y components, last eight years
IERS Bulletin A daily Earth orientation (USNO finals2000A.all) · U.S. Government work, public domain; cite IERS Bulletin A · 10/23/26
IERS Bulletin A daily Earth orientation (USNO finals2000A.all) · U.S. Government work, public domain; cite IERS Bulletin A · 10/23/26
Show the data as a table
Method and sources
The long series comes from IERS EOP 20 C04 (local copy, see data-pipeline/README.md), a combination of VLBI, GNSS, SLR and DORIS since 1962; recent values and predictions come from the USNO Bulletin A (finals2000A.all), where days marked P are predictions (dashed). Length of day is the excess over 86,400 SI seconds; UT1−UTC in seconds; polar motion in arcseconds.
Monthly and yearly means are computed on the server; the two LOD series (C04 and Bulletin A) are not merged.
Reading these data
Length-of-day variations have no established link with earthquakes or the Sun beyond atmospheric and oceanic angular momentum; correlations with ENSO and geomagnetic jerks are examined in Correspondences.
SOURCES OF THIS PAGE
- IERS Bulletin A daily Earth orientation (USNO finals2000A.all)
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IERS Rapid Service/Prediction Centre (USNO), Bulletin A: polar motion, UT1−UTC and length of day since 1973, with predictions (finals2000A.all).
· source page ↗
Licence : U.S. Government work, public domain; cite IERS Bulletin A · retrieved on Oct 23, 2026 · SHA-256 95a61292c957… - IERS EOP 20 C04 daily Earth orientation since 1962
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IERS Earth Orientation Centre, EOP 20 C04 (IAU2000A) combined series, 1962–; Bizouard, C., et al. (2019), J. Geod. 93, 621–633.
· doi:10.1007/s00190-018-1186-3 · source page ↗
Licence : IERS data, free use with citation (Bizouard et al., 2019) · retrieved on Oct 23, 2026 · SHA-256 395e94687b8a… - Gross (2000)
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Gross, R. S. (2000). The excitation of the Chandler wobble. Geophysical Research Letters, 27(15), 2329–2332.
· doi:10.1029/2000GL011450
Licence : Published literature; cited - Bizouard et al. (2019)
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Bizouard, C., Lambert, S., Gattano, C., Becker, O., & Richard, J.-Y. (2019). The IERS EOP 14C04 solution for Earth orientation parameters consistent with ITRF 2014. Journal of Geodesy, 93, 621–633.
· doi:10.1007/s00190-018-1186-3
Licence : Published literature; cited