{"uid":"cap_IBpsmorDb7uT09AF69oY0","slug":"gregorian-date-to-julian-day-number-converter-862b06bd","name":"Gregorian Date to Julian Day Number Converter","description":"Convert a proleptic-Gregorian calendar date to its Julian Day Number (the integer count of days since JDN 0, 1 January 4713 BC in the proleptic Julian calendar).","url":"https://datetime.openverbs.com/v1/to-jdn","method":"POST","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method","bodyType","body"],"properties":{"body":{"type":"object","required":["year","month","day"],"properties":{"day":{"type":"integer","maximum":31,"minimum":1},"year":{"type":"integer","maximum":9999,"minimum":1},"month":{"type":"integer","maximum":12,"minimum":1}},"additionalProperties":false},"type":{"type":"string","const":"http"},"method":{"enum":["POST"],"type":"string"},"bodyType":{"enum":["json","form-data","text"],"type":"string"}},"additionalProperties":false}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.004","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":"$0.004/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.004","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.004","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_kdFd-Y857lhMVjHndbizF","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.004","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Converts a proleptic-Gregorian calendar date (year, month, day) to its Julian Day Number (JDN), the integer count of days since JDN 0.","exampleAgentPrompt":"What is the Julian Day Number for July 4, 1776?","exampleUseCases":[{"title":"Astronomical event date lookup","prompt":"I need the Julian Day Number for January 1, 2000 — that's the J2000.0 epoch reference date used in astronomy."},{"title":"Historical date comparison","prompt":"Convert October 15, 1582 to its Julian Day Number so I can compare it to other historical dates using day-count arithmetic."},{"title":"Calendar interoperability for scheduling system","prompt":"Can you give me the JDN integer for March 20, 2025? I need to store it as a universal day count in my cross-calendar scheduling database."}],"resultDescription":"Returns the Julian Day Number (JDN) as an integer — the count of days elapsed since JDN 0, which corresponds to 1 January 4713 BC in the proleptic Julian calendar. This is a single integer value usable for day-count arithmetic across calendar systems.","failureModes":["Year out of range (must be 1–9999) returns a validation error","Month out of range (must be 1–12) returns a validation error","Day out of range (must be 1–31) returns a validation error","Missing required fields (year, month, or day) returns a schema error","Payment not provided or insufficient USDC balance returns a 402 error"],"whenToPreferThis":"Use this endpoint when you need a universal integer day count for a Gregorian date, particularly for astronomical calculations, cross-calendar arithmetic, historical date comparisons, or any system that requires a monotonically increasing day number. Prefer this over manual JDN formula implementations when accuracy and simplicity matter, and when integrating with other datetime.openverbs.com endpoints for chained date operations.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-15T00:45:57.008Z","isFirstParty":false}