Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 321
| Start | October 2, 1877 at 10:41 PM UTC |
|---|---|
| End | October 30, 1877 at 05:43 AM UTC |
| Length (days) | 27.29 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 316 | May 19, 1877 at 07:22 PM UTC | June 16, 1877 at 12:12 AM UTC | 27.20 |
| 317 | June 16, 1877 at 12:12 AM UTC | July 13, 1877 at 04:59 AM UTC | 27.20 |
| 318 | July 13, 1877 at 04:59 AM UTC | August 9, 1877 at 10:12 AM UTC | 27.22 |
| 319 | August 9, 1877 at 10:12 AM UTC | September 5, 1877 at 04:07 PM UTC | 27.25 |
| 320 | September 5, 1877 at 04:07 PM UTC | October 2, 1877 at 10:41 PM UTC | 27.27 |
| 321 | October 2, 1877 at 10:41 PM UTC | October 30, 1877 at 05:43 AM UTC | 27.29 |
| 322 | October 30, 1877 at 05:43 AM UTC | November 26, 1877 at 01:07 PM UTC | 27.31 |
| 323 | November 26, 1877 at 01:07 PM UTC | December 23, 1877 at 08:53 PM UTC | 27.32 |
| 324 | December 23, 1877 at 08:53 PM UTC | January 20, 1878 at 04:59 AM UTC | 27.34 |
| 325 | January 20, 1878 at 04:59 AM UTC | February 16, 1878 at 01:09 PM UTC | 27.34 |
| 326 | February 16, 1878 at 01:09 PM UTC | March 15, 1878 at 08:57 PM 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.