Julian Date Converter
"Julian date" means two different things — pick the one you need.
Advertisement
About this tool
The astronomical Julian Day Number counts days continuously since 4713 BC, used in astronomy. The YYDDD ordinal format (e.g. "26166" for the 166th day of 2026) is what manufacturing, food-safety and military systems usually mean by "Julian date"; some use the four-digit-year form YYYYDDD instead, and both are accepted.
Astronomers’ Julian Date starts at noon, so a calendar day’s Julian Day Number applies from midday UTC; at midnight the Julian Date ends in .5. The Modified Julian Date (MJD), used for satellites and in science, subtracts 2,400,000.5 so that it starts at midnight and has fewer digits.