Julian Date & Modified Julian Day Converter
Convert batches of Gregorian UTC dates to Julian dates and Modified Julian dates, or convert decimal Julian dates back to UTC.
Ready. Explore the example or use the input controls to begin.
Scope and practical limits
Years 0001–9999 and up to 500 rows. Uses the proleptic Gregorian calendar and UTC-based 86,400-second days. No historical calendar switch, UT1 or leap-second correction. Not precision astronomy software.
The tool processes your work in the browser. The website’s advertising and analytics follow its privacy and consent settings. Projects are not saved automatically. Media workspaces export their files directly rather than storing them in project JSON.
Using Julian Date & Modified Julian Day Converter
Julian dates start at noon. Modified Julian Date is JD minus 2400000.5.
- Start with the included example, or enter your own input.
- Adjust the settings and review the preview and any validation message.
- Download the result or save a project to continue later.
Example
2000-01-01T12:00:00Z corresponds to JD 2451545.0.
Questions & answers
Does Julian date mean the Julian calendar?
No. Julian date is a continuous day count. This tool interprets calendar input using proleptic Gregorian dates.
Is my project saved automatically?
No. Use Save project to keep an editable copy. Processing runs in the browser; site ads and analytics follow the website privacy and consent settings.
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