Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 1136
| Start | August 14, 1938 at 06:50 AM UTC |
|---|---|
| End | September 10, 1938 at 12:50 PM UTC |
| Length (days) | 27.25 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 1131 | March 31, 1938 at 04:07 AM UTC | April 27, 1938 at 10:32 AM UTC | 27.27 |
| 1132 | April 27, 1938 at 10:32 AM UTC | May 24, 1938 at 03:56 PM UTC | 27.23 |
| 1133 | May 24, 1938 at 03:56 PM UTC | June 20, 1938 at 08:44 PM UTC | 27.20 |
| 1134 | June 20, 1938 at 08:44 PM UTC | July 18, 1938 at 01:32 AM UTC | 27.20 |
| 1135 | July 18, 1938 at 01:32 AM UTC | August 14, 1938 at 06:50 AM UTC | 27.22 |
| 1136 | August 14, 1938 at 06:50 AM UTC | September 10, 1938 at 12:50 PM UTC | 27.25 |
| 1137 | September 10, 1938 at 12:50 PM UTC | October 7, 1938 at 07:27 PM UTC | 27.28 |
| 1138 | October 7, 1938 at 07:27 PM UTC | November 4, 1938 at 02:31 AM UTC | 27.29 |
| 1139 | November 4, 1938 at 02:31 AM UTC | December 1, 1938 at 09:58 AM UTC | 27.31 |
| 1140 | December 1, 1938 at 09:58 AM UTC | December 28, 1938 at 05:46 PM UTC | 27.33 |
| 1141 | December 28, 1938 at 05:46 PM UTC | January 25, 1939 at 01:54 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.