Conversion and verification
Get a value that would be tedious to compute manually.
Dates & time
Julian ↔ Gregorian date converter
Bidirectional Julian and Gregorian date conversion based on Julian day numbers, independent of country-specific adoption dates.
Julian ↔ Gregorian date converter
Convert a Gregorian calendar date to its Julian equivalent, or convert a Julian date back to Gregorian.
Result
Calendar and solar results are calculated locally in your browser.
Was this tool useful?
How does this tool work?
Convert a Gregorian calendar date to its Julian equivalent, or convert a Julian date back to Gregorian.
Both dates are linked through the Julian Day Number (JDN). The tool compares the calendar systems themselves and does not infer which reform date applied in a particular country. The result depends on the conventions of the calendar or phenomenon being calculated. The engine validates the entered values, applies the relevant conversion rules or astronomical formulas, and returns a localized result. For solar calculations, geographic position, time zone and date can materially change the output.
How to use this tool
Enter the inputs
Provide the requested date and values.
Adjust the context
Choose the conversion direction or location when required.
Read the result
The calculation runs locally and can be repeated with new values.
Use cases
Planning
Prepare a date, photo session or observation from precise inputs.
Documented comparison
Compare a date, light window or measurement with another source while keeping the calculation inputs and assumptions visible.
Tips and best practices
- Check the date and time zone for Sun-dependent calculations.
- For historical or official use, consider the local conventions described by the tool.
- Keep the inputs you used when you need to compare the result with another source or reproduce it later.
Frequently asked questions
Is the calculation sent to a server?
No. The engine runs directly in your browser.
Can I change the values and calculate again?
Yes. Adjust the inputs and run the calculation again immediately.
Why can the result differ from another website?
Two services may use slightly different conventions, astronomical thresholds or historical rules. Check the parameters and assumptions stated by each tool before comparing their results.
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