{"uid":"cap_EHF6j7_TsjZr-LIg8LDum","slug":"calendar-systems-gregorian-julian-date-converter-346ec136","name":"Calendar Systems – Gregorian / Julian Date Converter","description":"Convert between Gregorian and Julian calendar dates (Old Style / New Style) with the day difference for that date.","url":"https://calendar-systems.x402tookit.com/julian-calendar?utm_source=zero.xyz","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET"],"type":"string"},"queryParams":{"type":"object","required":["date"],"properties":{"date":{"type":"string","description":"YYYY-MM-DD, year 1 to 9999"},"from":{"enum":["gregorian","julian"],"type":"string","description":"gregorian (default) or julian: the calendar the date is written in"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"asOf":{"type":["null","string"]},"from":{"type":["null","string"]},"source":{"type":["null","string"]},"reasons":{"type":["array","null"],"items":{"type":"string"}},"summary":{"type":["null","string"]},"verdict":{"type":["null","string"]},"weekday":{"type":["null","string"]},"degraded":{"type":["boolean","null"]},"disclaimer":{"type":["null","string"]},"julianDate":{"type":["null","string"]},"notChecked":{"type":["array","null"],"items":{"type":"string"}},"dayDifference":{"type":["null","number"]},"gregorianDate":{"type":["null","string"]},"before1582Reform":{"type":["boolean","null"]}}}}}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.02","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.02/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_uuTTEkrvXqocmaPl29s9o","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.02","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Converts a date between the Gregorian (New Style) and Julian (Old Style) calendar systems, returning both dates and the day difference between them.","exampleAgentPrompt":"What is the Julian (Old Style) calendar date for October 15, 1582 Gregorian, and how many days apart are the two calendars on that date?","exampleUseCases":[{"title":"Historical document date reconciliation","prompt":"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?"},{"title":"Orthodox Easter date cross-reference","prompt":"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?"},{"title":"Pre-reform historical research","prompt":"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?"}],"resultDescription":"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.","failureModes":["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"],"whenToPreferThis":"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.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-29T13:08:04.405Z","isFirstParty":false,"canonicalSlug":"calendar-systems-gregorian-julian-date-converter-346ec136"}