Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 1157
| Start | March 9, 1940 at 07:18 AM UTC |
|---|---|
| End | April 5, 1940 at 02:31 PM UTC |
| Length (days) | 27.30 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 1152 | October 24, 1939 at 04:10 PM UTC | November 20, 1939 at 11:28 PM UTC | 27.30 |
| 1153 | November 20, 1939 at 11:28 PM UTC | December 18, 1939 at 07:08 AM UTC | 27.32 |
| 1154 | December 18, 1939 at 07:08 AM UTC | January 14, 1940 at 03:09 PM UTC | 27.33 |
| 1155 | January 14, 1940 at 03:09 PM UTC | February 10, 1940 at 11:20 PM UTC | 27.34 |
| 1156 | February 10, 1940 at 11:20 PM UTC | March 9, 1940 at 07:18 AM UTC | 27.33 |
| 1157 | March 9, 1940 at 07:18 AM UTC | April 5, 1940 at 02:31 PM UTC | 27.30 |
| 1158 | April 5, 1940 at 02:31 PM UTC | May 2, 1940 at 08:42 PM UTC | 27.26 |
| 1159 | May 2, 1940 at 08:42 PM UTC | May 30, 1940 at 01:55 AM UTC | 27.22 |
| 1160 | May 30, 1940 at 01:55 AM UTC | June 26, 1940 at 06:40 AM UTC | 27.20 |
| 1161 | June 26, 1940 at 06:40 AM UTC | July 23, 1940 at 11:33 AM UTC | 27.20 |
| 1162 | July 23, 1940 at 11:33 AM UTC | August 19, 1940 at 05:00 PM UTC | 27.23 |
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.