The three-digit code is ordinal, not astronomical
A day-of-year code numbers the days inside one calendar year. January 1 is 001, February 1 is 032 in a common year, and December 31 is 365 or 366 depending on whether the year is a leap year.
An astronomical Julian Date or Julian Day Number is a continuous count that does not reset on January 1. It is designed for comparing days across years and calendar systems, so it uses much larger values than ordinary production or logistics codes.
The confusion is common because some industries call ordinal day codes Julian dates. When precision matters, compare the terminology guide What Is a Julian Date? with the astronomical background in Why Astronomers Use Julian Day Numbers.
Why the year must travel with day-of-year values
The value 060 means a different civil date depending on the year. In a common year it maps to March 1, while in a leap year it maps to February 29. Without the year, the code is incomplete.
This is why many operational formats combine a four-digit year with a three-digit ordinal day. A value like 2026-181 is much safer than 181 by itself because the leap-year rule is attached to the input.
Choose the converter by the source label
If the source mentions astronomy, Julian Day, JD, or JDN, use a Julian Date converter. If it mentions a packaged date code, lot code, ordinal date, or day of year, first resolve the year and then map the ordinal day inside that year.
If the source says Julian calendar, it usually means the older civil calendar used before Gregorian reform in many places. That is a third case, and it should be handled with a Julian calendar converter instead of an astronomical day-count tool.