Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 1300
| Start | November 12, 1950 at 10:14 AM UTC |
|---|---|
| End | December 9, 1950 at 05:47 PM UTC |
| Length (days) | 27.31 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 1295 | June 29, 1950 at 03:40 AM UTC | July 26, 1950 at 08:34 AM UTC | 27.20 |
| 1296 | July 26, 1950 at 08:34 AM UTC | August 22, 1950 at 02:04 PM UTC | 27.23 |
| 1297 | August 22, 1950 at 02:04 PM UTC | September 18, 1950 at 08:16 PM UTC | 27.26 |
| 1298 | September 18, 1950 at 08:16 PM UTC | October 16, 1950 at 03:03 AM UTC | 27.28 |
| 1299 | October 16, 1950 at 03:03 AM UTC | November 12, 1950 at 10:14 AM UTC | 27.30 |
| 1300 | November 12, 1950 at 10:14 AM UTC | December 9, 1950 at 05:47 PM UTC | 27.31 |
| 1301 | December 9, 1950 at 05:47 PM UTC | January 6, 1951 at 01:42 AM UTC | 27.33 |
| 1302 | January 6, 1951 at 01:42 AM UTC | February 2, 1951 at 09:52 AM UTC | 27.34 |
| 1303 | February 2, 1951 at 09:52 AM UTC | March 1, 1951 at 05:57 PM UTC | 27.34 |
| 1304 | March 1, 1951 at 05:57 PM UTC | March 29, 1951 at 01:27 AM UTC | 27.31 |
| 1305 | March 29, 1951 at 01:27 AM UTC | April 25, 1951 at 07:57 AM UTC | 27.27 |
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.