Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 2200
| Start | January 27, 2018 at 06:40 AM UTC |
|---|---|
| End | February 23, 2018 at 02:49 PM UTC |
| Length (days) | 27.34 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 2195 | September 12, 2017 at 05:30 PM UTC | October 10, 2017 at 12:09 AM UTC | 27.28 |
| 2196 | October 10, 2017 at 12:09 AM UTC | November 6, 2017 at 07:15 AM UTC | 27.30 |
| 2197 | November 6, 2017 at 07:15 AM UTC | December 3, 2017 at 02:42 PM UTC | 27.31 |
| 2198 | December 3, 2017 at 02:42 PM UTC | December 30, 2017 at 10:32 PM UTC | 27.33 |
| 2199 | December 30, 2017 at 10:32 PM UTC | January 27, 2018 at 06:40 AM UTC | 27.34 |
| 2200 | January 27, 2018 at 06:40 AM UTC | February 23, 2018 at 02:49 PM UTC | 27.34 |
| 2201 | February 23, 2018 at 02:49 PM UTC | March 22, 2018 at 10:30 PM UTC | 27.32 |
| 2202 | March 22, 2018 at 10:30 PM UTC | April 19, 2018 at 05:16 AM UTC | 27.28 |
| 2203 | April 19, 2018 at 05:16 AM UTC | May 16, 2018 at 10:59 AM UTC | 27.24 |
| 2204 | May 16, 2018 at 10:59 AM UTC | June 12, 2018 at 03:55 PM UTC | 27.21 |
| 2205 | June 12, 2018 at 03:55 PM UTC | July 9, 2018 at 08:39 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.