Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 1278
| Start | March 22, 1949 at 02:59 PM UTC |
|---|---|
| End | April 18, 1949 at 09:43 PM UTC |
| Length (days) | 27.28 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 1273 | November 5, 1948 at 11:43 PM UTC | December 3, 1948 at 07:12 AM UTC | 27.31 |
| 1274 | December 3, 1948 at 07:12 AM UTC | December 30, 1948 at 03:02 PM UTC | 27.33 |
| 1275 | December 30, 1948 at 03:02 PM UTC | January 26, 1949 at 11:10 PM UTC | 27.34 |
| 1276 | January 26, 1949 at 11:10 PM UTC | February 23, 1949 at 07:19 AM UTC | 27.34 |
| 1277 | February 23, 1949 at 07:19 AM UTC | March 22, 1949 at 02:59 PM UTC | 27.32 |
| 1278 | March 22, 1949 at 02:59 PM UTC | April 18, 1949 at 09:43 PM UTC | 27.28 |
| 1279 | April 18, 1949 at 09:43 PM UTC | May 16, 1949 at 03:25 AM UTC | 27.24 |
| 1280 | May 16, 1949 at 03:25 AM UTC | June 12, 1949 at 08:20 AM UTC | 27.21 |
| 1281 | June 12, 1949 at 08:20 AM UTC | July 9, 1949 at 01:04 PM UTC | 27.20 |
| 1282 | July 9, 1949 at 01:04 PM UTC | August 5, 1949 at 06:11 PM UTC | 27.21 |
| 1283 | August 5, 1949 at 06:11 PM UTC | September 1, 1949 at 11:58 PM UTC | 27.24 |
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.