What this calculator does
What day of the year is it asks for a single number: counting from 1 January as day 1, which numbered day does a given date land on? This calculator takes any date and returns that day-of-year figure directly, along with how many days are left in the year and how far through the year that point falls as a percentage.
The day-of-year figure is used in places a plain calendar date is not: some payroll, scientific and logging systems record a date as a three-digit day-of-year number (sometimes called an ordinal date) rather than a month and day, and converting between the two by hand means counting through each preceding month.
The formula
The number of whole days between 31 December of the previous year and the date entered gives the day-of-year figure. Whether that date's year is a leap year decides if the year runs to 365 or 366 days, which affects both the total and the percentage-through-year figure for any date after February.
| Term | Meaning |
|---|---|
| Day of the year | The date's position counting from 1 January as day 1, running up to 365 or 366. |
| Ordinal date | Another name for a date written as a year and a day-of-year number instead of a month and day, used in some technical and logistics systems. |
| Leap year | A year with an extra day, 29 February, which shifts every day-of-year number after it forward by one compared with a non-leap year. |
The inputs explained
| Field | What to enter |
|---|---|
| Date to check | The date to check. Defaults to today. |
When to use it
Converting a calendar date to an ordinal date
Some inventory, shipping and payroll systems record dates as a day-of-year number rather than a month and day, so converting a normal date into that format, or back again, is a routine lookup.
Checking how far through the year a date falls
Progress tracking, whether for a yearly goal, a budget or a subscription period, is sometimes expressed as a percentage of the year elapsed, which this calculator reads off directly.
Working out how many days are left in the year from a specific date
Planning what can still be fit into the remainder of a year starts with knowing exactly how many days are left from a given point, not just an approximate month count.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
Which day of the year does a spread of dates fall on?
A spread of dates across the year, each converted to its day-of-year number and percentage through the year.
| Date | Day of the year | Percentage through the year |
|---|---|---|
| 2026-01-01 | 1 of 365 | 0.274% |
| 2026-03-15 | 74 of 365 | 20.3% |
| 2026-06-30 | 181 of 365 | 49.6% |
| 2026-09-22 | 265 of 365 | 72.6% |
| 2026-12-31 | 365 of 365 | 100.0% |
Questions
How is this different from the days in a year calculator?
The days in a year or month calculator covers a broader set of figures, including the days in the specific month and the leap year status. This calculator is focused purely on the day-of-year number itself, plus the percentage through the year, for whenever that single figure is what is actually needed.
Does the day-of-year number change in a leap year?
Yes, for any date from 1 March onwards. Since 29 February falls before those dates in a leap year, every day-of-year number from March onward is one higher than the same calendar date would show in a non-leap year.
What day of the year is 31 December?
Day 365 in a common year, or day 366 in a leap year, since it is always the last day of the year.
What is an ordinal date used for?
It is a compact way to record a date as a year and a single day-of-year number instead of a year, month and day, and turns up in some manufacturing date codes, payroll systems and scientific logging where sorting by a single number is convenient.
For the full day count of a year or month, including the leap year rule, see the days in a year or month calculator. For the ISO week number that same date falls in, use the week number calculator.