Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 64
| Start | July 25, 1858 at 06:29 AM UTC |
|---|---|
| End | August 21, 1858 at 12:00 PM UTC |
| Length (days) | 27.23 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 59 | March 11, 1858 at 02:30 AM UTC | April 7, 1858 at 09:37 AM UTC | 27.30 |
| 60 | April 7, 1858 at 09:37 AM UTC | May 4, 1858 at 03:41 PM UTC | 27.25 |
| 61 | May 4, 1858 at 03:41 PM UTC | May 31, 1858 at 08:49 PM UTC | 27.21 |
| 62 | May 31, 1858 at 08:49 PM UTC | June 28, 1858 at 01:33 AM UTC | 27.20 |
| 63 | June 28, 1858 at 01:33 AM UTC | July 25, 1858 at 06:29 AM UTC | 27.21 |
| 64 | July 25, 1858 at 06:29 AM UTC | August 21, 1858 at 12:00 PM UTC | 27.23 |
| 65 | August 21, 1858 at 12:00 PM UTC | September 17, 1858 at 06:13 PM UTC | 27.26 |
| 66 | September 17, 1858 at 06:13 PM UTC | October 15, 1858 at 01:00 AM UTC | 27.28 |
| 67 | October 15, 1858 at 01:00 AM UTC | November 11, 1858 at 08:12 AM UTC | 27.30 |
| 68 | November 11, 1858 at 08:12 AM UTC | December 8, 1858 at 03:46 PM UTC | 27.32 |
| 69 | December 8, 1858 at 03:46 PM UTC | January 4, 1859 at 11:42 PM UTC | 27.33 |
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.