Local Sidereal Time
Julian Date, GMST and LST from UTC and longitude — a developer-facing astronomy primitive
LST = GMST + longitude/15 hours. Intended as a primitive for other celestial mechanics work. Runs locally.
About this tool
Compute Julian Date, Greenwich Mean Sidereal Time and Local Sidereal Time from UTC and longitude. Copy JSON for other formulas. Local Sidereal Time runs in the browser on DevTools. There is no signup, and your input stays on this device unless the tool explicitly performs a live network lookup.
What this tool does not do
- Local Sidereal Time is a free in-browser utility, not a hosted API. It does not keep server-side history and is not a substitute for production verification in your own stack.
How do I use this tool?
How do I use Local Sidereal Time?
Open Local Sidereal Time, enter or paste your input, and copy the result. The page works without an account.
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