Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 550
| Start | November 9, 1894 at 12:00 AM UTC |
|---|---|
| End | December 6, 1894 at 07:32 AM UTC |
| Length (days) | 27.31 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 545 | June 25, 1894 at 05:37 PM UTC | July 22, 1894 at 10:30 PM UTC | 27.20 |
| 546 | July 22, 1894 at 10:30 PM UTC | August 19, 1894 at 03:57 AM UTC | 27.23 |
| 547 | August 19, 1894 at 03:57 AM UTC | September 15, 1894 at 10:07 AM UTC | 27.26 |
| 548 | September 15, 1894 at 10:07 AM UTC | October 12, 1894 at 04:51 PM UTC | 27.28 |
| 549 | October 12, 1894 at 04:51 PM UTC | November 9, 1894 at 12:00 AM UTC | 27.30 |
| 550 | November 9, 1894 at 12:00 AM UTC | December 6, 1894 at 07:32 AM UTC | 27.31 |
| 551 | December 6, 1894 at 07:32 AM UTC | January 2, 1895 at 03:26 PM UTC | 27.33 |
| 552 | January 2, 1895 at 03:26 PM UTC | January 29, 1895 at 11:35 PM UTC | 27.34 |
| 553 | January 29, 1895 at 11:35 PM UTC | February 26, 1895 at 07:42 AM UTC | 27.34 |
| 554 | February 26, 1895 at 07:42 AM UTC | March 25, 1895 at 03:15 PM UTC | 27.31 |
| 555 | March 25, 1895 at 03:15 PM UTC | April 21, 1895 at 09:50 PM 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.