Day of Year Calculator

About this calculator

The day-of-year (also called ordinal date or Julian day-of-year, not to be confused with the astronomical Julian Date) numbers every calendar date from 1 on January 1st up to 365 on December 31st in a common year, or 366 in a leap year — one determined by the standard Gregorian rule (divisible by 4, except century years unless divisible by 400).

This ordinal form is formalized in ISO 8601 as the YYYY-DDD date format, and it is widely used in programming, manufacturing date codes, agriculture and climate data, and payroll or scheduling systems where counting elapsed days within a year is more convenient than working with month and day separately.

Enter any date and this calculator returns its ordinal day number, the days remaining until year-end, and whether that year is a leap year.