Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 4155
| Start | January 25, 2164 at 08:15 AM UTC |
|---|---|
| End | February 21, 2164 at 04:26 PM UTC |
| Length (days) | 27.34 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 4150 | September 10, 2163 at 07:25 PM UTC | October 8, 2163 at 01:58 AM UTC | 27.27 |
| 4151 | October 8, 2163 at 01:58 AM UTC | November 4, 2163 at 09:00 AM UTC | 27.29 |
| 4152 | November 4, 2163 at 09:00 AM UTC | December 1, 2163 at 04:24 PM UTC | 27.31 |
| 4153 | December 1, 2163 at 04:24 PM UTC | December 29, 2163 at 12:10 AM UTC | 27.32 |
| 4154 | December 29, 2163 at 12:10 AM UTC | January 25, 2164 at 08:15 AM UTC | 27.34 |
| 4155 | January 25, 2164 at 08:15 AM UTC | February 21, 2164 at 04:26 PM UTC | 27.34 |
| 4156 | February 21, 2164 at 04:26 PM UTC | March 20, 2164 at 12:14 AM UTC | 27.32 |
| 4157 | March 20, 2164 at 12:14 AM UTC | April 16, 2164 at 07:11 AM UTC | 27.29 |
| 4158 | April 16, 2164 at 07:11 AM UTC | May 13, 2164 at 01:04 PM UTC | 27.25 |
| 4159 | May 13, 2164 at 01:04 PM UTC | June 9, 2164 at 06:07 PM UTC | 27.21 |
| 4160 | June 9, 2164 at 06:07 PM UTC | July 6, 2164 at 10:50 PM UTC | 27.20 |
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.