Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 425
| Start | July 9, 1885 at 04:00 PM UTC |
|---|---|
| End | August 5, 1885 at 09:09 PM UTC |
| Length (days) | 27.21 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 420 | February 23, 1885 at 10:26 AM UTC | March 22, 1885 at 06:03 PM UTC | 27.32 |
| 421 | March 22, 1885 at 06:03 PM UTC | April 19, 1885 at 12:44 AM UTC | 27.28 |
| 422 | April 19, 1885 at 12:44 AM UTC | May 16, 1885 at 06:21 AM UTC | 27.23 |
| 423 | May 16, 1885 at 06:21 AM UTC | June 12, 1885 at 11:15 AM UTC | 27.20 |
| 424 | June 12, 1885 at 11:15 AM UTC | July 9, 1885 at 04:00 PM UTC | 27.20 |
| 425 | July 9, 1885 at 04:00 PM UTC | August 5, 1885 at 09:09 PM UTC | 27.21 |
| 426 | August 5, 1885 at 09:09 PM UTC | September 2, 1885 at 02:58 AM UTC | 27.24 |
| 427 | September 2, 1885 at 02:58 AM UTC | September 29, 1885 at 09:27 AM UTC | 27.27 |
| 428 | September 29, 1885 at 09:27 AM UTC | October 26, 1885 at 04:26 PM UTC | 27.29 |
| 429 | October 26, 1885 at 04:26 PM UTC | November 22, 1885 at 11:47 PM UTC | 27.31 |
| 430 | November 22, 1885 at 11:47 PM UTC | December 20, 1885 at 07:30 AM UTC | 27.32 |
About this tool
A Carrington rotation is the time the Sun takes to turn once on its axis as seen from the Earth: 27.2753 days on average. The count was defined by the English astronomer Richard Carrington, who studied sunspots in the 1850s; rotation 1 began on 9 November 1853, and the numbering has run without interruption since.
Explorer computes the start of each rotation with the formula given by Jean Meeus in Astronomical Algorithms (chapter 29), implemented in its own astronomy library and checked against published dates. A rotation begins when the Carrington longitude L₀ of the central meridian passes through 0°; because the Earth moves along its orbit, the synodic period varies slightly around the mean, hence lengths of 27.2 to 27.3 days.
Observers use the rotation number as a calendar for the Sun: an active region that crosses the disc reappears about one rotation later, and the community activity heatmap shows one row per rotation so that returning regions line up. Enter a date to find its rotation, or a number to get the UTC start and end dates and the neighbouring rotations.