Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 7974
| Start | April 4, 2449 at 01:54 PM UTC |
|---|---|
| End | May 1, 2449 at 08:27 PM UTC |
| Length (days) | 27.27 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 7969 | November 18, 2448 at 10:41 PM UTC | December 16, 2448 at 06:13 AM UTC | 27.31 |
| 7970 | December 16, 2448 at 06:13 AM UTC | January 12, 2449 at 02:08 PM UTC | 27.33 |
| 7971 | January 12, 2449 at 02:08 PM UTC | February 8, 2449 at 10:18 PM UTC | 27.34 |
| 7972 | February 8, 2449 at 10:18 PM UTC | March 8, 2449 at 06:23 AM UTC | 27.34 |
| 7973 | March 8, 2449 at 06:23 AM UTC | April 4, 2449 at 01:54 PM UTC | 27.31 |
| 7974 | April 4, 2449 at 01:54 PM UTC | May 1, 2449 at 08:27 PM UTC | 27.27 |
| 7975 | May 1, 2449 at 08:27 PM UTC | May 29, 2449 at 01:57 AM UTC | 27.23 |
| 7976 | May 29, 2449 at 01:57 AM UTC | June 25, 2449 at 06:48 AM UTC | 27.20 |
| 7977 | June 25, 2449 at 06:48 AM UTC | July 22, 2449 at 11:34 AM UTC | 27.20 |
| 7978 | July 22, 2449 at 11:34 AM UTC | August 18, 2449 at 04:47 PM UTC | 27.22 |
| 7979 | August 18, 2449 at 04:47 PM UTC | September 14, 2449 at 10:42 PM UTC | 27.25 |
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.