Julian Date Converter
Convert date and time to Julian Date, Modified Julian Date, Unix timestamp, ISO 8601, and Julian calendar. Instant multi-system calendar conversion.
How It Works
Converts between standard Gregorian dates (MM/DD/YYYY) and Julian Dates (YYDDD). Julian dates represent the year and the continuous day of the year (1-365/366).
Formula
Julian Day (DDD) = Current Date - January 1st of Current Year + 1
The Julian date format YYDDD takes the last two digits of the year, and appends the day of the year.
Worked Example
Converting February 15, 2024 to Julian
- Year: 2024 (Leap year, YY = 24)
- Days in January: 31
- Days in February up to 15th: 15
- Day of Year (DDD) = 31 + 15 = 046
- Julian Date Format = 24046
Common Mistakes
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Forgetting leap years
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In a leap year, every date after February 28th shifts by 1 day. December 31st is day 366, not 365.
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Confusing Julian Date with Julian Period
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YYDDD is a continuous day-of-year format used in manufacturing. The Astronomical Julian Period (JD) counts days since 4713 BC.
