Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 3307
| Start | September 27, 2100 at 06:50 PM UTC |
|---|---|
| End | October 25, 2100 at 01:43 AM UTC |
| Length (days) | 27.29 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 3302 | May 14, 2100 at 04:02 PM UTC | June 10, 2100 at 09:02 PM UTC | 27.21 |
| 3303 | June 10, 2100 at 09:02 PM UTC | July 8, 2100 at 01:45 AM UTC | 27.20 |
| 3304 | July 8, 2100 at 01:45 AM UTC | August 4, 2100 at 06:47 AM UTC | 27.21 |
| 3305 | August 4, 2100 at 06:47 AM UTC | August 31, 2100 at 12:28 PM UTC | 27.24 |
| 3306 | August 31, 2100 at 12:28 PM UTC | September 27, 2100 at 06:50 PM UTC | 27.27 |
| 3307 | September 27, 2100 at 06:50 PM UTC | October 25, 2100 at 01:43 AM UTC | 27.29 |
| 3308 | October 25, 2100 at 01:43 AM UTC | November 21, 2100 at 09:00 AM UTC | 27.30 |
| 3309 | November 21, 2100 at 09:00 AM UTC | December 18, 2100 at 04:39 PM UTC | 27.32 |
| 3310 | December 18, 2100 at 04:39 PM UTC | January 15, 2101 at 12:39 AM UTC | 27.33 |
| 3311 | January 15, 2101 at 12:39 AM UTC | February 11, 2101 at 08:51 AM UTC | 27.34 |
| 3312 | February 11, 2101 at 08:51 AM UTC | March 10, 2101 at 04:49 PM UTC | 27.33 |
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.