Date to Day of Year Converter

Free day of year calculator. Convert any date to its ordinal day number (1-365 or 366). Essential for scheduling and programming.

Convert any calendar date to its ordinal day of the year (1-365, or 366 in leap years). January 1 is day 1, December 31 is day 365. Useful for programming, scheduling, and research.

Common use cases

  • Programming and data processing
  • Scientific data logging
  • Scheduling and planning systems
  • Date validation and conversion
  • Educational purposes

How to use

  1. Enter any date
  2. View the day of year (1-365/366)
  3. See if it's a leap year
  4. Calculate multiple dates quickly
  5. Copy the result

FAQ

What is day of year?

It's the count of days from January 1. March 1 is day 60 (or 61 in leap years).

Why use day of year?

It's useful in programming, science, and systems where sequential numbering simplifies calculations.

What about leap years?

Leap years have 366 days, affecting day numbers from March 1 onward.