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Calendar Systems – Gregorian / Julian Date Converter
x402
Calendar Systems – Gregorian / Julian Date Converter is a paid API for AI agents from calendar-systems.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-29).
Converts a date between the Gregorian (New Style) and Julian (Old Style) calendar systems, returning both dates and the day difference between them.
Price / call$0.02
Success—
StatusUnknown
How this service works
Convert between Gregorian and Julian calendar dates (Old Style / New Style) with the day difference for that date.
Output
Returns the input date expressed in both the Gregorian and Julian calendars (YYYY-MM-DD strings), the integer day difference between the two systems for that date, the weekday name, and a boolean indicating whether the date falls before the 1582 Gregorian reform, along with optional summary and disclaimer fields.
Example use cases
Historical document date reconciliation
“I found a letter dated March 25, 1700 in what appears to be Old Style Julian dating — what is the equivalent Gregorian (New Style) date, and how many days difference is there?”
Orthodox Easter date cross-reference
“Can you convert January 7, 2025 from the Julian calendar to its Gregorian equivalent so I can understand why Orthodox Christmas falls on that date?”
Pre-reform historical research
“I'm researching an event recorded as happening on September 2, 1752 in the Gregorian calendar — what was the Julian calendar date for that day, and was it before the 1582 reform?”
Technical details
Endpoint
GEThttps://calendar-systems.x402tookit.com/julian-calendar?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need to programmatically convert a specific date between the Gregorian and Julian calendar systems, especially for historical research, document dating, liturgical calendar cross-referencing, or any scenario where Old Style / New Style date reconciliation is required. It is purpose-built for this single conversion and returns the day difference directly, making it more reliable than general-purpose date libraries that may not handle pre-reform dates correctly.
Side effects
- Invalid date format (not YYYY-MM-DD) — returns error or null fields
- Date outside supported range (year 1–9999) — returns error
- Invalid 'from' enum value other than 'gregorian' or 'julian' — returns error
- Missing required 'date' query parameter — returns validation error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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