Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 1007
| Start | December 25, 1928 at 08:31 PM UTC |
|---|---|
| End | January 22, 1929 at 04:37 AM UTC |
| Length (days) | 27.34 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 1002 | August 11, 1928 at 09:46 AM UTC | September 7, 1928 at 03:43 PM UTC | 27.25 |
| 1003 | September 7, 1928 at 03:43 PM UTC | October 4, 1928 at 10:17 PM UTC | 27.27 |
| 1004 | October 4, 1928 at 10:17 PM UTC | November 1, 1928 at 05:19 AM UTC | 27.29 |
| 1005 | November 1, 1928 at 05:19 AM UTC | November 28, 1928 at 12:44 PM UTC | 27.31 |
| 1006 | November 28, 1928 at 12:44 PM UTC | December 25, 1928 at 08:31 PM UTC | 27.32 |
| 1007 | December 25, 1928 at 08:31 PM UTC | January 22, 1929 at 04:37 AM UTC | 27.34 |
| 1008 | January 22, 1929 at 04:37 AM UTC | February 18, 1929 at 12:47 PM UTC | 27.34 |
| 1009 | February 18, 1929 at 12:47 PM UTC | March 17, 1929 at 08:34 PM UTC | 27.32 |
| 1010 | March 17, 1929 at 08:34 PM UTC | April 14, 1929 at 03:29 AM UTC | 27.29 |
| 1011 | April 14, 1929 at 03:29 AM UTC | May 11, 1929 at 09:20 AM UTC | 27.24 |
| 1012 | May 11, 1929 at 09:20 AM UTC | June 7, 1929 at 02:22 PM UTC | 27.21 |
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.