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Julian Day Number Converter
Convert a proleptic Gregorian calendar date to its integer Julian Day Number and back.
ISO date or integer JDN
julian-day-number-converter.json (complete report and generated source where applicable)
Browser only
Runs locally in your browser. Your files, pasted content and generated output are not uploaded. Reset clears this tool’s working data.
This tool needs JavaScript. If it does not load, refresh the page and try again.
How to use this tool
- Enter values using the displayed examples; observe the documented input shape and limits.
- Choose Calculate result. Review the complete JSON report and any generated source text it contains.
- Download result to save the complete report; copy the generated source member into your project when relevant. Reset restores examples and clears output.
Examples
Direction: date-to-jdn
ISO date or integer JDN: 2000-01-01
Limitations
- Years 0001–9999. Integer JDN denotes calendar noon, not a timestamp or fractional astronomical Julian Date. No historical calendar switch.
- Maximum 100,000 UTF-16 units per field, 400,000 UTF-8 combined input bytes, 4 MiB output and 30 seconds in a local worker. Tool-specific bounds may be tighter.
- Generated snippets are source text inside the JSON download. They are never executed by this tool. Local inspection does not verify remote systems or establish standards certification.
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