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Gregorian & Julian Calendar Converter

Convert batches of Gregorian and Julian calendar dates with leap-rule validation, weekday checks and a shared integer-day index.

Purpose-built workspaceBrowser processingPreview before export

Ready. Explore the example or use the input controls to begin.

Scope and practical limits

Dates 0001–9999, up to 500 per batch. Both calendars are proleptic. Country-specific adoption gaps are not inferred. Results outside the supported year range are rejected. This converts calendar dates, not Julian Date time-of-day values.

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 Gregorian & Julian Calendar Converter

Convert batches of Gregorian and Julian calendar dates with leap-rule validation, weekday checks and a shared integer-day index.

Start with the example and set the relevant dates, range or clock settings.
Review validation messages and the calculated results, including calendar conventions and day offsets.
Download JSON or CSV; where available, export all-day calendar events. Save a project to retain your inputs.

Example

Gregorian 1582-10-15 maps to Julian 1582-10-05.
Julian 1900-02-29 is valid and maps to Gregorian 1900-03-13.

Questions & answers

Is the Julian calendar the same as Julian Date?

No. The Julian calendar has its own month and leap-year rules. Julian Date is a continuous day count; use the separate Julian Date converter for that task.

Does it account for when a country changed calendars?

No. It applies each calendar consistently across the supported years. Historical records may need country-specific interpretation.