BYTETOOLS

Day of Year Calculator

Find the day-of-year number (1–366) for any date, the days remaining in the year, and how far through the year you are as a percentage. Free and private.

236
Day of year
129
Days remaining
64.7%
Year elapsed
365
Days in year

This is a common year, so it has 365 days.

What is the Day of Year Calculator?

The ByteTools Day of Year Calculator converts any calendar date into its ordinal day number — a value from 1 (January 1) to 365 or 366 (December 31).

  • Ordinal day-of-year number (1–366)
  • Days remaining in the year
  • Percentage of the year elapsed
  • Leap-year aware total (365 vs 366 days)
  • One-click Today button
  • 100% in-browser — no uploads, works offline

How to use the Day of Year Calculator

  1. 1

    Pick a date (or click Today).

  2. 2

    Read the day-of-year number from 1 to 366.

  3. 3

    See how many days remain until the end of the year.

  4. 4

    Check the percentage of the year elapsed and whether it is a leap year.

About the Day of Year Calculator

The ByteTools Day of Year Calculator converts any calendar date into its ordinal day number — a value from 1 (January 1) to 365 or 366 (December 31). It also shows how many days remain in the year and the percentage of the year that has elapsed, giving a quick sense of progress.

Ordinal day-of-year values, sometimes loosely called Julian days, are widely used in science, agriculture, aviation, manufacturing lot codes and spreadsheet formulas. This tool makes the conversion instant and also tells you whether the year is a leap year, which decides between 365 and 366 total days.

All calculations run locally in your browser with JavaScript — nothing is uploaded, so it works offline and keeps your dates private.

Frequently asked questions

What is the day of the year?

The day of the year is a date's ordinal position counting from January 1 as day 1. For example March 1 is day 60 in a common year and day 61 in a leap year. December 31 is day 365, or day 366 in a leap year.

Is this the same as a Julian date?

In everyday use people call the ordinal day-of-year an "ordinal date" or loosely a "Julian day," and that is what this tool shows. True astronomical Julian Day is a different, continuous count of days since 4713 BC, which is not what most people mean.

How many days are in a year?

A common year has 365 days and a leap year has 366. The extra day, February 29, shifts every ordinal number from March onward by one, which is why the tool reports whether your year is a leap year.

How do I find how many days are left in the year?

The calculator subtracts the current day-of-year from the year's total (365 or 366). Pick any date and it shows the days remaining until December 31 of that year.

What is day-of-year used for?

It appears in scientific data logging, crop and weather records, aviation and shipping schedules, and manufacturing date codes, because a single number is easier to sort and compare than a full calendar date.

Guides for Day of Year Calculator

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