Day of Year Calculator
Find which day number of the year (1–366) any date falls on.
How to use this tool
- Enter date in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your day of year and the full breakdown beneath it.
Find which day number of the year (1–366) any date falls on.
How it works
The Day of Year Calculator tells you which day number a given date falls on within its year, on a scale of 1 (January 1) to 365 or 366 (December 31 in a leap year). This number is also called the ordinal date.
Knowing the day-of-year number is useful in agriculture (growing degree day calculations), military and government date coding, financial calculations involving day counts, and programming tasks where date arithmetic is performed on ordinal values.
The tool automatically accounts for leap years, so February 29 is valid on leap years, and March 1 falls on day 61 in a regular year but day 62 in a leap year.
Enter a date using the date picker and the ordinal day number is displayed instantly alongside the number of days remaining in the year.
Worked example
Find the ordinal date for a project deadline
- Select the deadline date (e.g., March 15) in the Date field.
- Read the day-of-year number shown.
- Use this number in your project scheduling spreadsheet or Gantt chart.
March 15 = day 74 in a non-leap year, day 75 in a leap year.
Common mistakes to avoid
- Confusing 'day of year' with 'Julian date' — they are different systems.
- Not checking whether the target year is a leap year before doing manual calculations with the ordinal number.
- Entering a date in the wrong format and getting an unexpected result — use the date picker to avoid format errors.
Key terms
- Ordinal date
- A date expressed as the year and the day number within that year, e.g., 2024-045 for February 14, 2024.
- Leap year
- A year with 366 days (February has 29 days), occurring in years divisible by 4, except century years not divisible by 400.
Frequently asked questions
- Is January 1 day 1 or day 0?
- January 1 is always day 1.