Day of the Year Calculator: Day 1 to 366
This day of the year calculator tells you which day number a date is, from 1 on January 1 to 365 or 366 on December 31. Pick a date and you also see how many days are left in the year, the ISO week number, the quarter, the weekday, whether it is a leap year and how far through the year you are. Switch to the second mode to turn a day number such as 200 into a calendar date for any year. It is handy for Julian dates in spreadsheets and logs, manufacturing date codes, agriculture and planting schedules, project planning and science data.
Day of the Year Calculator
Find the day number of any date, or turn a day number into a date. Shows days left, week and quarter.
How to use the Day of the Year Calculator
- Choose "Date to day number" or "Day number to date".
- Pick a date, or type a day number and a year.
- Read the day of the year, days left, week and quarter.
- Copy the result if you need it elsewhere.
Features
- Day number 1-366 with leap year handling
- Days left and percent of year passed
- ISO week number and quarter
- Day number back to a date
- Works for any year from 1 to 9999
- Copy the results
Frequently asked questions
What is the day of the year?
It is the count of days since January 1 of that year, where January 1 is day 1. December 31 is day 365, or day 366 in a leap year.
How do I find the day number by hand?
Add up the days in all the earlier months and add the day of the month. For March 15 in a common year that is 31 + 28 + 15 = 74.
Is this the same as a Julian date?
In many industries "Julian date" means year plus day of year, like 2026300. This tool gives that day number. The astronomical Julian Day Number is a different count that began in 4713 BC.
How do leap years change the number?
In a leap year February has 29 days, so every date from March 1 on is one day higher than in a common year. Leap years are divisible by 4, except century years not divisible by 400.
Which day number is today?
Open the tool and the date field starts on today's date, so the answer for today shows right away.