Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 4247
| Start | December 8, 2170 at 01:35 PM UTC |
|---|---|
| End | January 4, 2171 at 09:27 PM UTC |
| Length (days) | 27.33 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 4242 | July 25, 2170 at 04:47 AM UTC | August 21, 2170 at 10:10 AM UTC | 27.22 |
| 4243 | August 21, 2170 at 10:10 AM UTC | September 17, 2170 at 04:16 PM UTC | 27.25 |
| 4244 | September 17, 2170 at 04:16 PM UTC | October 14, 2170 at 10:58 PM UTC | 27.28 |
| 4245 | October 14, 2170 at 10:58 PM UTC | November 11, 2170 at 06:05 AM UTC | 27.30 |
| 4246 | November 11, 2170 at 06:05 AM UTC | December 8, 2170 at 01:35 PM UTC | 27.31 |
| 4247 | December 8, 2170 at 01:35 PM UTC | January 4, 2171 at 09:27 PM UTC | 27.33 |
| 4248 | January 4, 2171 at 09:27 PM UTC | February 1, 2171 at 05:36 AM UTC | 27.34 |
| 4249 | February 1, 2171 at 05:36 AM UTC | February 28, 2171 at 01:43 PM UTC | 27.34 |
| 4250 | February 28, 2171 at 01:43 PM UTC | March 27, 2171 at 09:20 PM UTC | 27.32 |
| 4251 | March 27, 2171 at 09:20 PM UTC | April 24, 2171 at 04:01 AM UTC | 27.28 |
| 4252 | April 24, 2171 at 04:01 AM UTC | May 21, 2171 at 09:39 AM UTC | 27.23 |
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.