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Day of Year Calculator

Enter a date to find its day number within the year.

Day of year

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Days remaining

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What this calculator does

This day of year calculator finds the ordinal day number of any date within its calendar year — for example, February 1 is always the 32nd day of the year. It also shows how many days remain in the year from that date.

Worked example

September 2, 2026 is the 245th day of 2026, with 120 daysremaining until the end of the year.

Common mistakes

  • Ignoring leap years. Dates from March onward shift up by one day-of-year number in a leap year compared to a non-leap year.
  • Confusing this with an astronomical Julian date. This is the day count within one calendar year (1–366), not the continuous Julian day number used in astronomy.
  • Off-by-one errors from manual counting. Manually adding up days per month is easy to get wrong — automated calculation avoids miscounting month lengths.

Frequently asked questions

What is a "day of year" number used for?+

Also called an ordinal date, it's used in programming, manufacturing date codes, agriculture, and scheduling systems where a single number is easier to sort and compare than a month/day pair.

Does a leap year change the day-of-year number?+

Yes — from March 1 onward, dates in a leap year have a day-of-year number one higher than the same calendar date in a non-leap year, because of the extra February 29.

What's the highest possible day-of-year number?+

365 in a standard year, or 366 in a leap year, both corresponding to December 31.

Is this the same as a Julian date used in astronomy?+

No — astronomical Julian dates count continuously from a fixed historical epoch. This calculator shows the ordinal day within a single calendar year (1–365 or 1–366), sometimes also loosely called a "Julian date" in manufacturing contexts.

Related calculators

Leap Year CheckerCheck instantly whether a year is a leap year. Days Between Two Dates CalculatorFind the exact number of days between two dates. Date CalculatorAdd or subtract days, weeks, months, or years from a date. Add or Subtract Days CalculatorAdd or subtract a number of days from a date.