Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 621
| Start | February 27, 1900 at 06:19 PM UTC |
|---|---|
| End | March 27, 1900 at 01:50 AM UTC |
| Length (days) | 27.31 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 616 | October 14, 1899 at 03:26 AM UTC | November 10, 1899 at 10:37 AM UTC | 27.30 |
| 617 | November 10, 1899 at 10:37 AM UTC | December 7, 1899 at 06:09 PM UTC | 27.31 |
| 618 | December 7, 1899 at 06:09 PM UTC | January 4, 1900 at 02:04 AM UTC | 27.33 |
| 619 | January 4, 1900 at 02:04 AM UTC | January 31, 1900 at 10:14 AM UTC | 27.34 |
| 620 | January 31, 1900 at 10:14 AM UTC | February 27, 1900 at 06:19 PM UTC | 27.34 |
| 621 | February 27, 1900 at 06:19 PM UTC | March 27, 1900 at 01:50 AM UTC | 27.31 |
| 622 | March 27, 1900 at 01:50 AM UTC | April 23, 1900 at 08:23 AM UTC | 27.27 |
| 623 | April 23, 1900 at 08:23 AM UTC | May 20, 1900 at 01:53 PM UTC | 27.23 |
| 624 | May 20, 1900 at 01:53 PM UTC | June 16, 1900 at 06:44 PM UTC | 27.20 |
| 625 | June 16, 1900 at 06:44 PM UTC | July 13, 1900 at 11:30 PM UTC | 27.20 |
| 626 | July 13, 1900 at 11:30 PM UTC | August 10, 1900 at 04:43 AM UTC | 27.22 |
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.