Free day of the year calculator
Find any date's day of the year in two seconds. Pick a date and the day of the year calculator returns its ordinal day number (1–366), how many days are left in the year, and the ISO 8601 ordinal date (YYYY-DDD) — with a cumulative-days table and a reverse day-number-to-date lookup, updated live, as you type.
On this page15 sections
| Month (the 1st) | 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 |
Counts whole days from 1 January (UTC), with leap years handled automatically. How it's calculated
Results are estimates. Consult a professional.
What is the day of the year?
The day of the year is a date's position counted from the start of its year: 1 January is day 1, and 31 December is day 365 in a common year or day 366 in a leap year. It is also called the ordinal date or ordinal day number. This day of the year calculator returns that number for any date you pick, along with how many days are left in the year and the inverse — the calendar date for any day number.
So if a date is the 61st day of the year, every day from 1 January up to and including that date has been counted. The international standard ISO 8601 writes this as an ordinal date in the form YYYY-DDD — a four-digit year, a hyphen, and the three-digit day number with leading zeros. For example, 1 March 2024 is written 2024-061.
How to calculate the day of the year
There are two ways to find the day of the year. The reliable one — and the one this calculator uses — counts whole days from 1 January. The shortcut adds up the lengths of the months before yours, which works but is easy to get wrong around February in a leap year.
The month-sum shortcut is: add the days in every month before the current one, then add the day of the month. For 1 March that is 31 (January) + 29 (February, leap year) + 1 = day 61. Use 28 for February in a common year and you get day 60 instead — which is exactly why a calculator that knows the leap-year rule is safer than counting by hand.
A worked example using the day of the year calculator
Sam needs the ordinal date for 1 March 2024 to label a batch in a YYDDD production code. 2024 is a leap year, so the count runs through a 29-day February — here is exactly how the calculator works it out.
Step 1 — Count the days in the months before March
January has 31 days and February 2024 has 29 (it is a leap year), so 31 + 29 = 60 days fall before March begins. That makes 29 February the 60th day of the year.
Step 2 — Add the day of the month
1 March adds one more day: 60 + 1 = 61. So 1 March 2024 is the 61st day of the year. (In a common year February has only 28 days, so the same date would be day 60.)
Step 3 — Read the days remaining and the ordinal date
2024 has 366 days in total, so the days remaining after 1 March are 366 − 61 = 305. The ISO 8601 ordinal date is written 2024-061.
What is an ordinal date?
Ordinal date is the formal name for the day of the year. An ordinal date pairs a year with the day number within it, so it pins down a date with just two values instead of the usual three (year, month, day). ISO 8601 — the international date standard — defines the written form as YYYY-DDD, with the day number always three digits and zero-padded.
| Calendar date | Day of year | ISO 8601 ordinal date |
|---|---|---|
| 1 January 2024 | 1 | 2024-001 |
| 10 April 2024 | 101 | 2024-101 |
| 1 March 2024 (leap) | 61 | 2024-061 |
| 1 March 2023 (common) | 60 | 2023-060 |
| 31 December 2024 (leap) | 366 | 2024-366 |
| 31 December 2023 (common) | 365 | 2023-365 |
The day number is always written as three digits (001–366). Leap years shift every date from 1 March onward one number later.
Cumulative days per month (leap vs common year)
To find any day of the year by hand, take the cumulative total for the start of its month and add the day of the month. The table below lists the day-of-year of the 1st of each month — so 1 March is day 60 in a common year and day 61 in a leap year. After February the two columns differ by exactly one, because of the leap day.
| Month (the 1st) | 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 |
Day-of-year of the 1st of each month. To get any date, add (day of month − 1). Example: 15 June (common) = 152 + 14 = day 166.
From 1 March onward the leap-year column is always one higher than the common-year column — the single extra day on 29 February ripples through the rest of the year. Up to and including 28 February the two are identical. Whether a year is a leap year follows the leap year rule.
How many days are left in the year?
Days remaining is the mirror image of the day of the year: it counts forward from a date to 31 December. The arithmetic is simple — days remaining = days in the year − day of the year — so the two always add up to 365 or 366.
This is the figure year-progress bars use: divide the day of the year by the total days to get the share of the year elapsed. To count down to a specific future date instead of the year-end, use the days between dates calculator.
Where ordinal dates and "Julian dates" are used
Day-of-year numbers turn up wherever a compact, sortable date helps. In manufacturing, food packaging, and the military, a code like 24061 or 2024061 — a two- or four-digit year followed by the three-digit day number — is stamped on products as a lot or pack date. Confusingly, the industry calls this a “Julian date,” even though it is really just the ordinal date described above.
- Food & manufacturing — pack and lot codes use YYDDD or YYYYDDD so a date sorts and prints in a few digits.
- IT & mainframes — COBOL, PL/I, and spreadsheet software historically stored an ordinal day-of-year; some legacy systems still call it a “Julian date.”
- Aviation & logistics — flight and shipment records use the day number to simplify date maths across a year.
- Science & agriculture — day of year (often abbreviated DOY) is the standard x-axis for seasonal data like growing-degree days and climate records.
Convert a day number back to a date
The calculator also works in reverse: give it a year and a day number and it returns the calendar date. This is the inverse lookup — useful for decoding a YYDDD lot code or reading a day-of-year value out of a dataset back into a familiar date.
Note how the same day number maps to a different date depending on the year: day 61 is 1 March in a leap year but 2 March in a common year, because the missing 29 February shifts everything from March onward. That is why an ordinal date is only meaningful alongside its year.
Common day-of-the-year questions
What number day of the year is it?
Pick today's date in the calculator and it returns the day number instantly — 1 for 1 January, up to 365 or 366 for 31 December. The day count is shown alongside the days remaining in the year and the ISO 8601 ordinal date.
How many days are in a year?
365 in a common year and 366 in a leap year. The extra day is 29 February, which appears only in leap years and makes that year's highest day number 366 instead of 365.
What is the highest possible day of the year?
366, which falls on 31 December of a leap year. In a common year the highest is 365, also on 31 December. There is no day 0 — the count starts at 1 on 1 January.
How this calculator works and sources
This day of the year calculator counts whole days from 1 January of the date's year, in UTC, so the result never shifts across timezones and leap years are handled automatically. The ordinal-date concept and its YYYY-DDD written form are defined by ISO 8601; the leap-year rule is the standard Gregorian one (divisible by 4, except century years not divisible by 400). The maths runs entirely in your browser — the date you enter is never sent anywhere.
Frequently asked questions about the free day of the year calculator
About this day of the year calculator
This day of the year calculator runs entirely in your browser. The date you pick never leaves your device — nothing is sent to a server, logged, or shared. It counts whole days from January 1 in UTC, so the day number is stable across timezones and leap years are handled automatically, updating instantly on every change.
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