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Stargazing Auxiliary
Astronomical Time Converter
Convert local time to UTC, Julian date and local sidereal time.
Try the tool
Local time: 2026/8/29 16:24:49
Universal time (UTC): 2026-08-29 08:24:49 UTC
Julian date: 2461281.85058
Local sidereal time: 06:55
Tool principle
Local sidereal time uses the standard GMST formula (Meeus, Ch. 12) plus observer longitude.
Data source: Native algorithm.
User guide
- 1Enter your longitude (east positive, west negative).
- 2All values update once per second.
- 3Use sidereal time to know which right ascension is on your meridian right now.
Frequently asked questions
Why sidereal time?＋
Stars return to the meridian every 23h 56m — sidereal time tracks that rotation exactly.