📆 Day of Year Calculator

Find which numbered day of the year any date falls on — or find the date for a given day number.

DAY NUMBER OF THE YEAR
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Days Remaining
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Week Number
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Leap Year?
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Percent of Year
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What Is a "Day of Year" Number?

The day of year (sometimes called an ordinal date or, less precisely, a "Julian date") simply numbers each day sequentially from January 1st (day 1) through December 31st (day 365, or 366 in a leap year). It's widely used in manufacturing date codes, agriculture and farming schedules, payroll and fiscal systems, and programming.

Day of year = number of days elapsed since Jan 1 of that year, plus 1 Leap years (366 days) occur in years divisible by 4, except centuries not divisible by 400

Leap Years and This Calculator

This tool automatically accounts for leap years using the standard Gregorian calendar rule: a year is a leap year if it's divisible by 4, unless it's also divisible by 100 — unless it's also divisible by 400 (so 2000 was a leap year, but 1900 was not). That means dates after February in a leap year shift by one day number compared to a non-leap year.

Common Uses

📎 Related Tools: Day of the Week Calculator Date Calculator Days Until Calculator Age Calculator

❓ Frequently Asked Questions

What day number is December 31st?
December 31st is day 365 in a regular year, or day 366 in a leap year.
Does this calculator account for leap years?
Yes — it uses the standard Gregorian leap year rule (divisible by 4, except century years not divisible by 400) to correctly calculate day numbers for any year you enter.
What's the difference between 'day of year' and 'Julian date'?
In everyday use, people often call this a "Julian date," but the true astronomical Julian Date is a continuous day count since 4713 BC used in astronomy. What this calculator computes is more precisely called the "ordinal date" or "day of year" — the sequential day number within a single calendar year.
Why do some product date codes use day-of-year numbers?
Manufacturing and food industries often stamp products with a Julian-style day-of-year code (e.g., "26034" for the 34th day of 2026) because it's compact and unambiguous for tracking production and expiration dates across systems.
Can I find the date for a specific day number in a past or future year?
Yes — switch to the "Day Number → Date" tab, enter the day number and the year, and the calculator will show the corresponding calendar date, correctly accounting for whether that year is a leap year.

🏆 About This Tool — Accuracy & Trust

🔒 Data Privacy: All calculations run entirely within your browser using JavaScript. Nothing you enter here is ever transmitted to our servers, stored, sold, or shared.

📐 Accuracy Note: This tool uses standard, widely published formulas and guidelines. Results are estimates for informational purposes; for financial, medical, or engineering decisions, consult a licensed professional.

📅 Last Updated: September 2026.