Day of Year
Find a date’s day number of the year (1 to 366), the days in that year and the days left, or turn a day number back into a date. It opens on today. How it works
Use the Day of Year
About the Day of Year
The day of the year counts from 1 on January 1 to 365 on December 31, or to 366 in a leap year. October 14, 2026 is day 287 of 365 with 78 days left, and March 1 is day 60 in 2026 but day 61 in 2024. Pick a date and the page shows its day number, the length of that year, the days that remain after it and its weekday, or switch Convert to Day number to date to turn a day number back into a date: day 100 of 2025 is April 10.
Day number of the first day of each month
| Month | Common year, such as 2026 | Leap year, such as 2024 |
|---|---|---|
| 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 |
Counted with the calculator’s own day-number function. From March on, a leap year is one day ahead because February has 29 days.
Which date is day 100, 200, 250, 300 and 365
| Day number | 2026 (365 days) | 2024 (366 days) |
|---|---|---|
| 100 | April 10 | April 9 |
| 200 | July 19 | July 18 |
| 250 | September 7 | September 6 |
| 300 | October 27 | October 26 |
| 365 | December 31 | December 30 |
Each date is what Day number to date returns for that year and day number, and entering the date returns the day number again.
How to use this tool
- The date field opens on today’s date once the page has loaded. Pick or type another date to replace it.
- Read the day number, the number of days in that year (365 or 366), the days left after the date and its weekday: March 1, 2025 is a Saturday.
- Clear the field to clear the result. A link ending in ?date=2024-12-31 opens the page on that date.
- To find the date for a day number, set Convert to Day number to date and type the year (1000 to 9999) and the day (1 to 366). The date, its weekday and its ISO form appear.
Frequently asked questions
- What day of the year is October 14, 2026?
- Day 287 of 365, with 78 days left after it. In a leap year the same date sits one day later in the count: October 14, 2024 is day 288 of 366.
- What is the day number of December 31?
- It is 365 in a common year such as 2026 and 366 in a leap year such as 2024, and the page shows it as “out of 365” or “out of 366”. Leap years are the years divisible by 4, except years divisible by 100 that are not divisible by 400, so 2100 has 365 days and 2000 had 366.
- Which date is day 100, day 200 or day 300?
- Set Convert to Day number to date, type the year and the day number, and the page shows the date. In 2026 day 100 is April 10, day 200 is July 19 and day 300 is October 27. In a leap year such as 2024 each falls one calendar day earlier: April 9, July 18 and October 26.
- Is the day of the year the same as a Julian date?
- Not in the astronomical sense. ISO 8601 writes a year plus a day number from 1 to 366 as an ordinal date, YYYY-DDD, so 2026-287 is October 14, 2026. The older label “Julian date” for that number is confused with the Julian day number that astronomers use, which counts days continuously and is a different value. Check which one a document means.
- How many days are left in the year after a date?
- The page shows it under the day number: 365 or 366 minus the day number. After October 14, 2026 there are 78 days left, and after December 31 there are 0.
- What day of the year is it today?
- Open the page and the date field fills in with today’s date from your device. The large number is today’s day number, the line under it says out of 365 or out of 366, and the days left in the year follow.
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