Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 241
| Start | October 12, 1871 at 10:20 PM UTC |
|---|---|
| End | November 9, 1871 at 05:30 AM UTC |
| Length (days) | 27.30 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 236 | May 29, 1871 at 06:21 PM UTC | June 25, 1871 at 11:06 PM UTC | 27.20 |
| 237 | June 25, 1871 at 11:06 PM UTC | July 23, 1871 at 03:59 AM UTC | 27.20 |
| 238 | July 23, 1871 at 03:59 AM UTC | August 19, 1871 at 09:26 AM UTC | 27.23 |
| 239 | August 19, 1871 at 09:26 AM UTC | September 15, 1871 at 03:36 PM UTC | 27.26 |
| 240 | September 15, 1871 at 03:36 PM UTC | October 12, 1871 at 10:20 PM UTC | 27.28 |
| 241 | October 12, 1871 at 10:20 PM UTC | November 9, 1871 at 05:30 AM UTC | 27.30 |
| 242 | November 9, 1871 at 05:30 AM UTC | December 6, 1871 at 01:02 PM UTC | 27.31 |
| 243 | December 6, 1871 at 01:02 PM UTC | January 2, 1872 at 08:56 PM UTC | 27.33 |
| 244 | January 2, 1872 at 08:56 PM UTC | January 30, 1872 at 05:05 AM UTC | 27.34 |
| 245 | January 30, 1872 at 05:05 AM UTC | February 26, 1872 at 01:12 PM UTC | 27.34 |
| 246 | February 26, 1872 at 01:12 PM UTC | March 24, 1872 at 08:44 PM UTC | 27.31 |
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.