Right now (UTC): ordinal Julian date — · Julian Day —
Convert a calendar date to a Julian date — either the ordinal day-of-year form (the 5-digit code like 26206 used on packaging and lot numbers) or the astronomical Julian Day (JD) used in science — and convert either one back. Everything runs in your browser.
Right now (UTC): ordinal Julian date — · Julian Day —
Two very different things share the name "Julian date". This tool handles both.
Ordinal Julian date (day of year). This is what most people outside astronomy mean. It's the day's position in the year — 1 to 365 or 366 — usually written as a five-digit YYDDD code (the last two digits of the year plus the three-digit day). For example, 25 July 2026 is the 206th day of the year, so its Julian date is 26206. You'll see it stamped on food packaging and pharmaceuticals, in manufacturing lot codes, on shipping labels and in older mainframe systems. Some systems use the seven-digit YYYYDDD form instead, e.g. 2026206.
Astronomical Julian Day (JD). Astronomers and programmers use the Julian Day: a single continuous count of days (and fractions of a day) since noon Universal Time on 1 January 4713 BC. Today it's around 2,461,000. Because it never resets and ignores months and leap years, it makes calculating the time between two events trivial — you just subtract. The Julian Day Number (JDN) is the integer part (the whole day starting at noon), and the Modified Julian Day (MJD = JD − 2,400,000.5) is a shorter version that starts each day at midnight, used widely in satellite and space data.
Choose "Julian date (day-of-year)" for the ordinal/packaging format, or "Julian Day (astronomical)" for the scientific JD.
Type a calendar date to get the Julian value, or type a Julian value to get the calendar date — the conversion runs both ways and updates instantly.
The result shows every form you might need — day of year, 5-digit and 7-digit codes, or JD, JDN and MJD with the UTC time.
Related: Military time converter · Date calculator · Week number · Days in a year
YYDDD code such as 26206 for the 206th day of 2026. In astronomy, the Julian Date (JD) is a continuous count of days since noon on 1 January 4713 BC. This converter does both.26206. It is widely used on food packaging, in manufacturing lot codes and on legacy mainframe systems. Some systems use the 7-digit form (YYYYDDD), e.g. 2026206.001 every 1 January and only names a day within a year, which is why the 5-digit code carries the two-digit year in front of the day number. The astronomical Julian Day never resets — it is one ever-increasing number, around 2,461,000 today, that also carries the time of day as a fraction, so subtracting two JDs gives an exact elapsed time. Use the day-of-year tab for packaging and lot codes, and the Julian Day tab for science and date arithmetic.