Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 4257
| Start | September 7, 2171 at 06:16 AM UTC |
|---|---|
| End | October 4, 2171 at 12:44 PM UTC |
| Length (days) | 27.27 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 4252 | April 24, 2171 at 04:01 AM UTC | May 21, 2171 at 09:39 AM UTC | 27.23 |
| 4253 | May 21, 2171 at 09:39 AM UTC | June 17, 2171 at 02:33 PM UTC | 27.20 |
| 4254 | June 17, 2171 at 02:33 PM UTC | July 14, 2171 at 07:18 PM UTC | 27.20 |
| 4255 | July 14, 2171 at 07:18 PM UTC | August 11, 2171 at 12:26 AM UTC | 27.21 |
| 4256 | August 11, 2171 at 12:26 AM UTC | September 7, 2171 at 06:16 AM UTC | 27.24 |
| 4257 | September 7, 2171 at 06:16 AM UTC | October 4, 2171 at 12:44 PM UTC | 27.27 |
| 4258 | October 4, 2171 at 12:44 PM UTC | October 31, 2171 at 07:43 PM UTC | 27.29 |
| 4259 | October 31, 2171 at 07:43 PM UTC | November 28, 2171 at 03:04 AM UTC | 27.31 |
| 4260 | November 28, 2171 at 03:04 AM UTC | December 25, 2171 at 10:47 AM UTC | 27.32 |
| 4261 | December 25, 2171 at 10:47 AM UTC | January 21, 2172 at 06:51 PM UTC | 27.34 |
| 4262 | January 21, 2172 at 06:51 PM UTC | February 18, 2172 at 03:02 AM UTC | 27.34 |
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.