Skip to content

Tools

EN

Day of the Year

Which number a date holds in its year, how many days are left, and how much of the year has gone.

—

Days remaining—
Of the year elapsed—

Counting days straight through, and what a leap year does to it

The day of the year is the plain sequential count from 1 January. It ignores months entirely, which is the point: it turns a date into a single number you can subtract, sort or plot without dragging a calendar along. Astronomers, accountants and agronomists all reach for it for that reason, and in agriculture it is the ordinary way to record a sowing or a harvest, because “day 100” compares across years in a way that “10 April” does not.

Leap years are where the count stops being obvious. Through February the numbers agree, but from 1 March onward every date shifts by one: 1 March is day 60 in a common year and day 61 in a leap year, and the gap persists to the end of December. So day 100 is 10 April in an ordinary year and 9 April in a leap year, and day 200 is 19 July or 18 July. Any table that maps day numbers to dates without asking which year it is will be wrong for ten months out of twelve, three years in four.

The complement is often what people actually want. If today is day 224 of 365, then 141 days remain and 61.4% of the year has elapsed — useful for a quarterly target, a project burn-down or simply knowing where you stand. Note that this number is not the “Julian day” of astronomy, which counts continuously from 4713 BC and is in the millions; the shorthand “Julian date” for a day-of-year number is common in industry and means this one.

Frequently asked questions

What day of the year is it?

Enter a date above to see its number, from 1 to 365 or 366. Today is filled in by default and computed in your browser, so it is right the moment you load the page rather than at the moment the page was built.

How do I calculate the day of the year by hand?

Add the lengths of the complete months before yours, then add the day of the month. For 10 April: 31 + 28 + 31 = 90, plus 10 gives day 100. In a leap year add one more from March onward, since February contributes 29.

Why does a leap year change the number?

Because 29 February is inserted before the rest of the year. Every date from 1 March to 31 December moves up by one, so the same calendar date carries a different day number depending on the year. Dates in January and February are unaffected.

What is the last day of the year?

31 December is day 365 in a common year and day 366 in a leap year. It is the one date whose number tells you immediately whether the year was a leap year.

Is this the same as the Julian day number?

No, though the names collide. The astronomical Julian day counts continuously from 1 January 4713 BC and is currently over 2.4 million. The number here restarts at 1 every January. Manufacturing and logistics often call this one a “Julian date”, which is where the confusion comes from.

Other tools