Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 1929
| Start | November 1, 1997 at 12:51 PM UTC |
|---|---|
| End | November 28, 1997 at 08:15 PM UTC |
| Length (days) | 27.31 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 1924 | June 18, 1997 at 07:20 AM UTC | July 15, 1997 at 12:06 PM UTC | 27.20 |
| 1925 | July 15, 1997 at 12:06 PM UTC | August 11, 1997 at 05:20 PM UTC | 27.22 |
| 1926 | August 11, 1997 at 05:20 PM UTC | September 7, 1997 at 11:15 PM UTC | 27.25 |
| 1927 | September 7, 1997 at 11:15 PM UTC | October 5, 1997 at 05:49 AM UTC | 27.27 |
| 1928 | October 5, 1997 at 05:49 AM UTC | November 1, 1997 at 12:51 PM UTC | 27.29 |
| 1929 | November 1, 1997 at 12:51 PM UTC | November 28, 1997 at 08:15 PM UTC | 27.31 |
| 1930 | November 28, 1997 at 08:15 PM UTC | December 26, 1997 at 04:01 AM UTC | 27.32 |
| 1931 | December 26, 1997 at 04:01 AM UTC | January 22, 1998 at 12:07 PM UTC | 27.34 |
| 1932 | January 22, 1998 at 12:07 PM UTC | February 18, 1998 at 08:17 PM UTC | 27.34 |
| 1933 | February 18, 1998 at 08:17 PM UTC | March 18, 1998 at 04:05 AM UTC | 27.32 |
| 1934 | March 18, 1998 at 04:05 AM UTC | April 14, 1998 at 11:01 AM UTC | 27.29 |
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.