Day of the Year Calculator

Pick a date to see its ordinal day (for example, day 290 of 365), the number of days remaining after it, the percentage of the year elapsed, and whether the year is a leap year. Details add the day of the week, the calendar quarter and the ISO 8601 week with its week-year.

The day number is the UTC difference between the selected date and January 1, plus one. Days remaining counts the days after the selected date up to December 31. Year elapsed is the day number divided by the days in the year (365 or 366) times 100, rounded to two decimals, so December 31 always shows 100%.

The calculation uses only the calendar date, never a local time of day, so a daylight-saving change or your time zone cannot move a date to the previous or next day. Today uses the date shown by your device clock.

Leap years follow the Gregorian rule: divisible by 4, except century years that are not divisible by 400. 2000 and 2024 are leap years; 1900 and 2100 are not. ISO 8601 weeks start on Monday and week 1 contains the first Thursday of the year, which is why January 1 can fall in week 52 or 53 of the previous week-year. Dates before 1582 use the proleptic Gregorian calendar.