This kind of count — expressing a date as a single running number instead of a month-and-day pair — is often called an “ordinal date” or “day-of-year number.” January 1st is always day 1, and the count simply increases by one for every day that passes, with no reset until the calendar rolls over to a new year.
How the count works
To find the day of the year by hand, add up the lengths of every month before the current one and then add today’s day of the month. For March 10 in a common year:
The top of the range
In a common year, December 31st is day 365. In a leap year, the extra day at the end of February pushes everything after it forward by one, so December 31st becomes day 366 instead. That single day of drift is why leap-year and common-year day numbers don’t line up for the second half of the year.
Where day-of-year numbers show up
Manufacturers stamp them on packaging as part of “Julian date” codes so a product’s day of production can be read from a compact number. Some scheduling and inventory systems use them internally because comparing two single numbers is simpler than comparing two month-and-day pairs. They’re also a quick way to answer “roughly what fraction of the year has passed” — day 91 is about a quarter of the way through a common year, day 273 is roughly three-quarters.
Day-of-year chart
The day number of the first and last day of every month. Leap years add one from March onward (and to February 29 itself):
| Month | 1st (common year) | 1st (leap year) | Last day (common) | Last day (leap) |
|---|---|---|---|---|
| January | 1 | 1 | 31 | 31 |
| February | 32 | 32 | 59 | 60 |
| March | 60 | 61 | 90 | 91 |
| April | 91 | 92 | 120 | 121 |
| May | 121 | 122 | 151 | 152 |
| June | 152 | 153 | 181 | 182 |
| July | 182 | 183 | 212 | 213 |
| August | 213 | 214 | 243 | 244 |
| September | 244 | 245 | 273 | 274 |
| October | 274 | 275 | 304 | 305 |
| November | 305 | 306 | 334 | 335 |
| December | 335 | 336 | 365 | 366 |
Which date is day number N?
| Day number | Common year (e.g. 2026) | Leap year (e.g. 2028) |
|---|---|---|
| 50 | February 19 | February 19 |
| 100 | April 10 | April 9 |
| 150 | May 30 | May 29 |
| 200 | July 19 | July 18 |
| 250 | September 7 | September 6 |
| 256 | September 13 | September 12 |
| 300 | October 27 | October 26 |
| 365 | December 31 | December 30 |
Day 256 is celebrated as Programmers’ Day, because 256 is 2 to the 8th power.
Related counts
The number on this page is recalculated from your device’s local date each time you load it. To see the count from the other direction, use how many days are left in the year. For the week-based equivalents, see what week of the year it is and how many weeks are left. To confirm the underlying calendar date, check today’s date.