Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 831
| Start | November 4, 1915 at 08:01 AM UTC |
|---|---|
| End | December 1, 1915 at 03:27 PM UTC |
| Length (days) | 27.31 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 826 | June 21, 1915 at 02:13 AM UTC | July 18, 1915 at 07:01 AM UTC | 27.20 |
| 827 | July 18, 1915 at 07:01 AM UTC | August 14, 1915 at 12:19 PM UTC | 27.22 |
| 828 | August 14, 1915 at 12:19 PM UTC | September 10, 1915 at 06:19 PM UTC | 27.25 |
| 829 | September 10, 1915 at 06:19 PM UTC | October 8, 1915 at 12:56 AM UTC | 27.28 |
| 830 | October 8, 1915 at 12:56 AM UTC | November 4, 1915 at 08:01 AM UTC | 27.29 |
| 831 | November 4, 1915 at 08:01 AM UTC | December 1, 1915 at 03:27 PM UTC | 27.31 |
| 832 | December 1, 1915 at 03:27 PM UTC | December 28, 1915 at 11:16 PM UTC | 27.33 |
| 833 | December 28, 1915 at 11:16 PM UTC | January 25, 1916 at 07:24 AM UTC | 27.34 |
| 834 | January 25, 1916 at 07:24 AM UTC | February 21, 1916 at 03:33 PM UTC | 27.34 |
| 835 | February 21, 1916 at 03:33 PM UTC | March 19, 1916 at 11:16 PM UTC | 27.32 |
| 836 | March 19, 1916 at 11:16 PM UTC | April 16, 1916 at 06:05 AM UTC | 27.28 |
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.