Find the Julian date of any day, and print the Julian date calendar for the year.

A Julian date on a package is the day of the year, counted from 001 on January 1.

Julian date = days in the months before + day of the month

Count January 1 as day 1, and every date after it gets the next number. January has 31 days, so February 1 is day 032. In a normal year March 1 is 060, July 1 is 182 and December 31 is 365. The tool prints the number with leading zeros so it always has three digits, and the table under it shows the number for every date of the year.

The same number turns up in three lengths. Take the example date, Monday, November 2, 2026.

• DDD is the plain day of the year, 306
• YYDDD adds the last two digits of the year in front, 26306
• YYYYDDD adds all four, 2026306, and ISO 8601 writes the same thing as 2026-306

The code box in the tool reads all three. Type 26306 and it finds November 2, 2026; type 306 and it uses the year you have chosen. The five-digit form is read as 20YY, so 26306 is 2026 and never 1926.

Egg cartons print the day the eggs were packed as a three-digit Julian date.

The USDA's shell egg day of the year chart gives the examples “001 = January 1st”, “049 = February 18th” and “198 = July 17th”. The tool agrees with all three: day 49 of 2026 is February 18 and day 198 is July 17. The same coding is common on lot and batch codes in factories and warehouses, where a short number that sorts in order is easier to print than a date.

Reading a code needs only the table. Find 198 in the grid and the row says July and the column says 17. Press Print in the tool and only the table goes to paper, without the page around it, so it can be pinned up.

Leap years move every date after February 28 up by one day.

February 29 is day 060 in a leap year, so March 1 becomes 061 instead of 060, and December 31 is 366. In 2026 March 1 is day 060; in 2028 it is day 061. January and February never change. If a code was written in a leap year and you read it against a normal-year table, every date after February comes out one day late, which is the most common slip when a three-digit code is checked by hand. The tool takes the year from the date you pick, and from the Year of the calendar box for the table.

The same date has three different Julian numbers, and they are easy to mix up.

“Julian date” means different things in different trades, and a search for it brings back all three. The tool lists each one under the day of the year.

• The day of the year is what packaging, food and factories use, and what the big number at the top of the tool shows.
• The Julian day number counts whole days in one run since 4713 BC, a count astronomers and software use so two dates can be subtracted. The U.S. Naval Observatory's Julian date converter and formula page describe it. Midnight at the start of November 2, 2026 is Julian date 2461346.5, because the count turns over at noon, and the tool also shows the modified Julian date, 61346.
• The Julian calendar is the Roman calendar that came before the one we use. From March 14, 1900 to March 13, 2100 its dates run 13 days behind ours, so November 2, 2026 is October 20 there, and January 7, 2027, the date of Orthodox Christmas, is December 25, 2026.

Use the year table to check a code, plan a production run or pin up a calendar.

The table has one row per day of the month and one column per month, so a date is where its row and its column meet. Days that do not exist, such as February 30, are left blank. The Year of the calendar box moves the table to any year from 1900 to 2100, and the selected date is highlighted so it is easy to find. For the gap between two dates, the days between dates calculator subtracts them, and the date calculator counts forward or back from one. The week number calculator gives the week of the year if your records count in weeks instead of days.

A date on a code is only useful if someone is there to act on it.

A batch code tells you when something was made. It says nothing about who made it, and a line that runs on two people who know the process fails the same way whatever the code says. TeamPredict reads public LinkedIn signals to flag resignation risk early, so the gap shows up as a warning while there is still time to talk.