Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 2242
| Start | March 17, 2021 at 10:35 PM UTC |
|---|---|
| End | April 14, 2021 at 05:32 AM UTC |
| Length (days) | 27.29 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 2237 | November 1, 2020 at 07:21 AM UTC | November 28, 2020 at 02:45 PM UTC | 27.31 |
| 2238 | November 28, 2020 at 02:45 PM UTC | December 25, 2020 at 10:31 PM UTC | 27.32 |
| 2239 | December 25, 2020 at 10:31 PM UTC | January 22, 2021 at 06:37 AM UTC | 27.34 |
| 2240 | January 22, 2021 at 06:37 AM UTC | February 18, 2021 at 02:48 PM UTC | 27.34 |
| 2241 | February 18, 2021 at 02:48 PM UTC | March 17, 2021 at 10:35 PM UTC | 27.32 |
| 2242 | March 17, 2021 at 10:35 PM UTC | April 14, 2021 at 05:32 AM UTC | 27.29 |
| 2243 | April 14, 2021 at 05:32 AM UTC | May 11, 2021 at 11:25 AM UTC | 27.25 |
| 2244 | May 11, 2021 at 11:25 AM UTC | June 7, 2021 at 04:28 PM UTC | 27.21 |
| 2245 | June 7, 2021 at 04:28 PM UTC | July 4, 2021 at 09:11 PM UTC | 27.20 |
| 2246 | July 4, 2021 at 09:11 PM UTC | August 1, 2021 at 02:11 AM UTC | 27.21 |
| 2247 | August 1, 2021 at 02:11 AM UTC | August 28, 2021 at 07:50 AM UTC | 27.24 |
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.