Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 1761
| Start | April 16, 1985 at 01:38 PM UTC |
|---|---|
| End | May 13, 1985 at 07:25 PM UTC |
| Length (days) | 27.24 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 1756 | November 30, 1984 at 10:58 PM UTC | December 28, 1984 at 06:47 AM UTC | 27.33 |
| 1757 | December 28, 1984 at 06:47 AM UTC | January 24, 1985 at 02:54 PM UTC | 27.34 |
| 1758 | January 24, 1985 at 02:54 PM UTC | February 20, 1985 at 11:03 PM UTC | 27.34 |
| 1759 | February 20, 1985 at 11:03 PM UTC | March 20, 1985 at 06:47 AM UTC | 27.32 |
| 1760 | March 20, 1985 at 06:47 AM UTC | April 16, 1985 at 01:38 PM UTC | 27.29 |
| 1761 | April 16, 1985 at 01:38 PM UTC | May 13, 1985 at 07:25 PM UTC | 27.24 |
| 1762 | May 13, 1985 at 07:25 PM UTC | June 10, 1985 at 12:24 AM UTC | 27.21 |
| 1763 | June 10, 1985 at 12:24 AM UTC | July 7, 1985 at 05:08 AM UTC | 27.20 |
| 1764 | July 7, 1985 at 05:08 AM UTC | August 3, 1985 at 10:11 AM UTC | 27.21 |
| 1765 | August 3, 1985 at 10:11 AM UTC | August 30, 1985 at 03:54 PM UTC | 27.24 |
| 1766 | August 30, 1985 at 03:54 PM UTC | September 26, 1985 at 10:17 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.