Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 928
| Start | February 1, 1923 at 04:44 AM UTC |
|---|---|
| End | February 28, 1923 at 12:49 PM UTC |
| Length (days) | 27.34 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 923 | September 17, 1922 at 03:12 PM UTC | October 14, 1922 at 09:57 PM UTC | 27.28 |
| 924 | October 14, 1922 at 09:57 PM UTC | November 11, 1922 at 05:07 AM UTC | 27.30 |
| 925 | November 11, 1922 at 05:07 AM UTC | December 8, 1922 at 12:39 PM UTC | 27.31 |
| 926 | December 8, 1922 at 12:39 PM UTC | January 4, 1923 at 08:34 PM UTC | 27.33 |
| 927 | January 4, 1923 at 08:34 PM UTC | February 1, 1923 at 04:44 AM UTC | 27.34 |
| 928 | February 1, 1923 at 04:44 AM UTC | February 28, 1923 at 12:49 PM UTC | 27.34 |
| 929 | February 28, 1923 at 12:49 PM UTC | March 27, 1923 at 08:21 PM UTC | 27.31 |
| 930 | March 27, 1923 at 08:21 PM UTC | April 24, 1923 at 02:54 AM UTC | 27.27 |
| 931 | April 24, 1923 at 02:54 AM UTC | May 21, 1923 at 08:25 AM UTC | 27.23 |
| 932 | May 21, 1923 at 08:25 AM UTC | June 17, 1923 at 01:15 PM UTC | 27.20 |
| 933 | June 17, 1923 at 01:15 PM UTC | July 14, 1923 at 06:02 PM UTC | 27.20 |
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.