Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 1966
| Start | August 6, 2000 at 05:45 PM UTC |
|---|---|
| End | September 2, 2000 at 11:33 PM UTC |
| Length (days) | 27.24 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 1961 | March 23, 2000 at 02:35 PM UTC | April 19, 2000 at 09:18 PM UTC | 27.28 |
| 1962 | April 19, 2000 at 09:18 PM UTC | May 17, 2000 at 02:58 AM UTC | 27.24 |
| 1963 | May 17, 2000 at 02:58 AM UTC | June 13, 2000 at 07:53 AM UTC | 27.20 |
| 1964 | June 13, 2000 at 07:53 AM UTC | July 10, 2000 at 12:37 PM UTC | 27.20 |
| 1965 | July 10, 2000 at 12:37 PM UTC | August 6, 2000 at 05:45 PM UTC | 27.21 |
| 1966 | August 6, 2000 at 05:45 PM UTC | September 2, 2000 at 11:33 PM UTC | 27.24 |
| 1967 | September 2, 2000 at 11:33 PM UTC | September 30, 2000 at 06:00 AM UTC | 27.27 |
| 1968 | September 30, 2000 at 06:00 AM UTC | October 27, 2000 at 12:58 PM UTC | 27.29 |
| 1969 | October 27, 2000 at 12:58 PM UTC | November 23, 2000 at 08:18 PM UTC | 27.31 |
| 1970 | November 23, 2000 at 08:18 PM UTC | December 21, 2000 at 04:01 AM UTC | 27.32 |
| 1971 | December 21, 2000 at 04:01 AM UTC | January 17, 2001 at 12:04 PM 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.