📆 Day of the Year Calculator
By ToolNimba Editorial Team · Updated 2026-06-19
Pick a date to see its day-of-year number, how many days are left in the year, and the percentage of the year that has elapsed.
This day of year calculator tells you the ordinal day number for any date, from 1 on January 1 up to 365 or 366 on December 31. Enter a date, or just use today, and you will instantly see the day-of-year number, how many days remain in the year, the percentage of the year that has elapsed, and the weekday. Leap years are handled automatically, so the count is always correct for the year you pick.
What is the Day of Year Calculator?
The day of the year, also called the ordinal date, is simply the position of a date counted from the start of its year. January 1 is day 1, February 1 is day 32, and December 31 is day 365 in a common year or day 366 in a leap year. It is a compact way to refer to a date without naming the month, which is why it shows up in astronomy, agriculture, aviation, and many computer and data systems where dates are stored as a year plus a day number.
Leap years are the one wrinkle. A year is a leap year if it is divisible by 4, except for century years, which must also be divisible by 400. So 2024 and 2000 are leap years, but 1900 and 2100 are not. In a leap year, February has 29 days, which pushes every date from March 1 onward up by one compared with a common year. March 1 is day 60 in a common year but day 61 in a leap year, and the total length of the year is 366 days instead of 365. This calculator checks the leap rule for the exact year you enter, so the day number, the days remaining, and the percentage are all based on the right total.
The days remaining figure is the number of days left until the end of that year, counted as total days in the year minus the current day number. The percentage elapsed is the day number divided by the total days in the year, times 100. Because the count is inclusive (the chosen day itself is already counted as elapsed), January 1 sits at roughly 0.27% rather than 0%, and December 31 lands at exactly 100%. These three figures together give you a quick sense of where any date falls within its year.
When to use it
- Answering "what day number is it?" for today or any past or future date.
- Converting a calendar date into an ordinal date (year plus day number) for data files, logs, or scientific records.
- Tracking progress through the year, for example seeing what percentage of the year is gone for goals or reporting.
- Working out how many days are left in the year for planning, countdowns, or year-end deadlines.
How to use the Day of Year Calculator
- Enter a date, or click Today to use the current date.
- Read the day-of-year number (1 to 365, or 1 to 366 in a leap year).
- Check the days remaining and the percentage of the year that has elapsed.
- Note the weekday and whether the year is a leap year or a common year.
Formula & method
Worked examples
Find the day of year for June 19, 2026 (a common year).
- 2026 is not divisible by 4, so it is a common year with 365 days.
- Add the lengths of the months before June: 31 + 28 + 31 + 30 + 31 = 151 days (Jan to May).
- Add the day in June: 151 + 19 = 170.
- Days remaining = 365 - 170 = 195.
- Percent elapsed = 170 ÷ 365 x 100 = 46.58%.
Result: Day 170 of 365, 195 days remaining, 46.58% of the year elapsed.
Find the day of year for March 1, 2024 (a leap year).
- 2024 is divisible by 4 and is not a century year, so it is a leap year with 366 days.
- Add the lengths of the months before March: 31 (Jan) + 29 (Feb) = 60 days.
- Add the day in March: 60 + 1 = 61.
- Days remaining = 366 - 61 = 305.
- Percent elapsed = 61 ÷ 366 x 100 = 16.67%.
Result: Day 61 of 366, 305 days remaining, 16.67% of the year elapsed.
Day of year for the first of each month (common year vs leap year)
| Date | Common year | Leap year |
|---|---|---|
| January 1 | 1 | 1 |
| February 1 | 32 | 32 |
| March 1 | 60 | 61 |
| April 1 | 91 | 92 |
| May 1 | 121 | 122 |
| June 1 | 152 | 153 |
| July 1 | 182 | 183 |
| August 1 | 213 | 214 |
| September 1 | 244 | 245 |
| October 1 | 274 | 275 |
| November 1 | 305 | 306 |
| December 1 | 335 | 336 |
| December 31 | 365 | 366 |
Common mistakes to avoid
- Forgetting that leap years shift everything after February. From March 1 onward, the day number in a leap year is one higher than in a common year, because February has 29 days. Using a fixed table for every year gives the wrong answer for leap years. This tool checks the actual year you enter.
- Treating every century year as a leap year. A common shortcut is "divisible by 4 means leap year", but century years are the exception: they must also be divisible by 400. So 2000 is a leap year while 1900 and 2100 are not.
- Counting January 1 as day 0. The ordinal date is one-based, so January 1 is day 1, not day 0. The days remaining and percentage here use this inclusive count, which is why the chosen day is treated as already elapsed.
- Confusing day of year with day of week or week number. The day of year is a number from 1 to 366. It is not the weekday (Monday to Sunday) nor the ISO week number (1 to 53). Use the matching calculator if you need those instead.
Glossary
- Day of year
- The position of a date counted from January 1, where January 1 is day 1 and December 31 is day 365 or 366.
- Ordinal date
- A date written as a year plus a day-of-year number, for example 2026-170 for June 19, 2026.
- Leap year
- A year with 366 days, having a February 29. A year is a leap year if divisible by 4, except century years, which must be divisible by 400.
- Common year
- An ordinary 365-day year, with no February 29.
- Days remaining
- The number of days left in the year after the chosen date, equal to the total days in the year minus the day-of-year number.
Frequently asked questions
What is the day of the year?
The day of the year, or ordinal date, is the position of a date counted from the start of its year. January 1 is day 1, and December 31 is day 365 in a common year or day 366 in a leap year. It is a way to refer to a date using just a number.
How many days are in a leap year?
A leap year has 366 days because February has 29 days instead of 28. A common (non-leap) year has 365 days. The calculator detects which type the year is and counts against the correct total.
How do I know if a year is a leap year?
A year is a leap year if it is divisible by 4, with one exception: century years (those ending in 00) must also be divisible by 400. So 2024 and 2000 are leap years, but 1900 and 2100 are not.
What day number is it today?
Click the Today button and the calculator fills in the current date and shows its day-of-year number straight away, along with the days remaining and the percentage of the year that has elapsed.
How is the percentage of the year calculated?
It is the day-of-year number divided by the total number of days in that year, multiplied by 100. The count is inclusive, so the chosen day is already counted as elapsed. December 31 lands at exactly 100%.
Why does March 1 have a different day number in a leap year?
Because February has 29 days in a leap year instead of 28, every date from March 1 onward shifts up by one. March 1 is day 60 in a common year but day 61 in a leap year.