Date math
Day of the Year Calculator
Find the day number for any date - out of 365 or 366.
Day 1-366 Leap-year aware Instant
What is a Day of the Year Calculator?
A Day of the Year Calculator tells you the ordinal number of any date - its position from 1 (January 1) through 365 or 366 (December 31). It's also called the day-of-year number or, in industry, a Julian date, and it's a compact way to say exactly where a date falls in the year - "day 220 of 365," for example.
The format is popular in logistics, manufacturing, and project planning because a single number removes any month ambiguity. This calculator also shows how many days remain in the year and what percentage of the year has already passed.
Example: picking August 8, 2026 → Day 220 of 365 - 60% of the year complete, with 145 days remaining.
How to Use the Day of the Year Calculator
Pick any date and click Find Day of Year. The result shows the day number, the total days in that year (365 or 366), the days remaining until December 31, and the percentage of the year elapsed so far.
Use the Today preset for the current day, or Jan 1 and Dec 31 to see the year's boundaries. The Leap Day preset jumps to February 29, 2024 - a date that only exists in leap years and demonstrates the 366-day count.
Common Uses
- Project tracking - "We're on day 45 of a 100-day sprint"
- Streak challenges - Reading or fitness goals measured as "day 75 of 365"
- Manufacturing date codes - Food, tires, and batteries stamp a 3-digit Julian day
- Fiscal and academic calendars - Track progress through a custom year
- New Year's resolutions - See exactly how much of the year is behind you
- Pregnancy milestones - Gestational age is often tracked in days
How the Day of the Year Is Counted
The count always starts at 1 on January 1. A common year has 365 days, so December 31 lands on day 365. A leap year adds February 29, pushing the total to 366 - which means every date from March 1 onward lands one day higher than it would in a non-leap year.
This ordinal count is different from a week number, which
groups days into 52-53 Monday-start weeks, and from the weekday,
which only names the day of the week. A closely related industry term is the
Julian date - a 3- or 4-digit form like 220 or 20220
meaning the 220th day of 2026, stamped on packaging to encode a manufacture date without
spelling out a month.
Frequently Asked Questions
What is the current day of the year?
Tap the Today button above to see the current day of the year. The number runs from 1 on January 1 to 365 (or 366 in a leap year) on December 31, then resets.
How is the day of the year calculated?
January 1 is counted as day 1, and every date that follows adds one. For example, day 100 of 2026 is April 10. In a leap year, the extra February 29 shifts every later day up by one.
How many days are in the year 2026?
2026 has 365 days, because it is not a leap year. Leap years such as 2024 and 2028 have 366 days. You can check any year with our Leap Year Calculator.
Is January 1 day 1 or day 0?
January 1 is day 1 - the count starts at one, not zero. December 31 is therefore day 365 in a common year, or day 366 in a leap year.
What is day 60 of a leap year?
In a leap year, day 60 is February 29 - the leap day itself. Because of that extra day, March 1 becomes day 61 instead of day 60, and every date after February is one higher than in a common year.
What's the difference between day of year and week number?
The day of year counts individual days from 1 to 365 or 366. A week number groups those days into 52 or 53 ISO weeks. For the week a date belongs to, use our Week Number Calculator.