Calendar date → Julian date
Julian date code → calendar date
Two different things called "Julian date"
The ordinal date (YYDDD). Year plus day-of-year. The US military, food manufacturers and many batch-coding systems use it because it is short and sorts in order. Day 001 is 1 January; see the day-of-year table for every number. ISO 8601 writes the same idea as 2026-045.
The Julian Day (JD). Astronomers count days continuously from noon UTC on 1 January 4713 BC, so the gap between any two observations is a simple subtraction. The fraction after the decimal point is the time of day, with .0 at noon. The Modified Julian Date (MJD = JD − 2400000.5) starts at midnight and is used by satellite and geodesy software.
Questions people ask
What is today's Julian date?
In the ordinal sense (used by the military, food packaging and manufacturing) it is the two-digit year followed by the three-digit day of the year, shown at the top of this page. Astronomers use the Julian Day Number instead, also shown.
How do I read a Julian date code on food packaging?
A five-digit code like 26045 usually means 2026, day 45 (14 February). Some manufacturers use a single year digit (6045) or add a plant code, so check the maker's key if the numbers don't fit.
What is the Julian Day Number?
A continuous count of days used in astronomy, starting from noon on 1 January 4713 BC (Julian calendar). Joseph Scaliger proposed the period in 1583. 1 January 2000 at noon UTC was JD 2451545.0.
Is the Julian date related to the Julian calendar?
Only by name. The Julian calendar is Julius Caesar's calendar (still used by some Orthodox churches), which currently runs 13 days behind the Gregorian. Our date converter handles it.