About this day of the year calculator
The day of the year, also called the ordinal date, counts days from 1 January, which is day 1, to 31 December, which is day 365, or day 366 in a leap year. It is used in manufacturing and shipping codes, scientific data, food packaging, and the ISO 8601 ordinal format such as 2026-277. This calculator gives the day number of any date from year 1 to 9999, along with the days already passed and still left, a progress bar for the year, the ISO week and quarter, the meteorological season in both hemispheres, and the zodiac sign. A reference table shows the day number on which each month starts in common and leap years.
How to find the day of the year
- Pick a date. Choose any date, or press Today or another quick date.
- Press Find day number. Read the day number and the days passed and left in that year.
- Check the details. See the ISO week, quarter, season, and a calendar of the month, and use the table to look up other dates by hand.
Frequently asked questions
How do I work out the day of the year by hand?
Add the days in all the months before your date, then add the day of the month. For 4 October in a common year, January to September have 273 days, so 4 October is day 277.
What changes in a leap year?
February has 29 days, so every date from 1 March onward is one day number higher than in a common year, and the year ends on day 366.
What is an ordinal date?
It is the ISO 8601 way of writing a date as year and day number, such as 2026-277. It is compact and sorts correctly, which is why it appears in logs and data files.
Is the day number the same as a Julian date?
In business and manufacturing, “Julian date” often means this day number, as in 26277. In astronomy, the Julian Date is a different count of days since 4713 BC.
Which day of the year is 1 July?
In a common year 1 July is day 182, and in a leap year it is day 183. The middle of a common year falls on 2 July, day 183.