Find a date’s position in the year
The day of the year is a running count starting with 1 January as day one. It turns the uneven months into one number, from 1 through 365 in a common year or 1 through 366 in a leap year. Use it to read an ordinal date, check a yearly milestone, or understand how far a calendar year has progressed.
Choose the full date
The year is needed because leap years change the numbering after February.
Calculate the day number
Read the selected date’s position and the total number of days in that year.
Check the remaining days and percentage
The supporting line shows days after the selected date and a percentage that includes that date.
Common-year and leap-year examples
| Date | Common year | Leap year |
|---|---|---|
| 1 January | Day 1 | Day 1 |
| 28 February | Day 59 | Day 59 |
| 29 February | Not a valid date | Day 60 |
| 1 March | Day 60 | Day 61 |
| 31 December | Day 365 | Day 366 |
For example, 14 September 2026 is day 257 of a 365-day year. There are 108 days after that date, and including 14 September places the year at about 70.4 percent. The three figures describe the same position in different ways: an ordinal number, a remaining count, and a share of the whole year.
What “days remaining” includes
The remaining count excludes the selected date. On 31 December it is zero, even though that calendar day may not yet have ended. This is a date-based calculation, not a live clock measuring the precise fraction of the year elapsed. If you need a ticking display to a particular time on New Year’s Day, use countdown.
Reading ordinal date notation
An ISO ordinal date combines the year with a three-digit day number. For example, 2026-257 means day 257 of 2026, or 14 September. Leading zeros keep early values consistent: 1 January is written as day 001. Keep the year with the day number, since day 060 refers to different month-and-day dates in common and leap years.
This calculator takes an ordinary calendar date and shows its day number. It does not provide a reverse ordinal-date input. When checking a code on packaging or a record, confirm the publisher’s format; a compact string of digits may use a different convention or a shortened year.
Do not confuse ordinal dates with Julian Dates
Some industries informally call a day-of-year number a “Julian date”. Astronomers use Julian Date for a different continuous day count that does not restart each January. Always establish which meaning a document uses before comparing values. The ordinal dates guide explains the difference and common uses.
Comparing dates across New Year
Subtracting day numbers works within the same year, but the count restarts on 1 January. Across a year boundary, compare the complete dates with date difference. For leap-year rules, see leap years explained; the extra February day affects every later ordinal number in that year.