Twenty-four solar terms
Find the instants at which the apparent solar longitude reaches each multiple of 15 degrees during a Gregorian year.
Your inputs
Start with the example values, then replace them with your own. For tables, keep the vertical bar separators and use a dot for decimals.
This simplified educational calculation has stated assumptions. Do not use it for navigation, engineering safety or other safety-critical decisions.
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Result and workspace
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How it works
Use the twenty-four apparent solar longitude crossings at 0, 15, …, 345 degrees. Search the entire Gregorian year and sort the UTC instants. This describes astronomical solar terms; local calendar dates depend on the time zone.
Worked example
These sample results use the original example inputs in the form. They do not change when you edit your inputs; your own result appears in the workspace.
- Events: 24
| UTC instant | Solar longitude |
|---|---|
| 2026-01-05T08:23:03.114Z | 285 |
| 2026-01-20T01:44:42.360Z | 300 |
| 2026-02-03T20:01:54.541Z | 315 |
| 2026-02-18T15:51:32.389Z | 330 |
Read the result carefully
Results depend on the values and assumptions shown above. Change one input at a time to see its effect. A blank or unavailable result means the data does not support a calculation; it is not zero.