To find what day of the year it is, number the days from January 1 (day 1) to December 31 (day 365, or 366 in a leap year) and see where today falls. The year progress tracker shows today’s number live, along with how much of the year is done and how many days are left.
The day of the year, also called the day number or ordinal date, is used in production date codes, logs, data files and planning. This guide shows how to work it out by hand with a month-by-month table, explains the “Julian date” codes such as 27105 that you see on packaging and in older computer systems, clears up the confusion with the astronomers’ Julian Day, and shows how to get the days left in the year.
Today’s day number: use the year progress tracker
The year progress page gives today’s day of the year out of 365 or 366, the percentage of the year that’s complete, the ISO week, the days and working days left, and the year’s halfway point. It counts today as a day that’s done, so January 1 is day 1 and December 31 shows the year 100% complete. For a single date in another year, the day of the week calculator gives the weekday, and the table below gets you the day number in seconds.
How day-of-year numbering works
The rules are short:
- January 1 is day 1. There’s no day 0.
- Days are numbered straight through the year without restarting each month, so February 1 is day 32.
- A common year ends on day 365. A leap year ends on day 366, because February 29 is day 60 and every later date moves up by one.
So the same date has a different day number in a leap year from March 1 onward. April 15 is day 105 in 2027, but in 2028, a leap year, day 105 is April 14 and April 15 is day 106. If you’re decoding a number rather than a date, you need to know the year.
First day of each month: day numbers
To find any date’s number, take the first-of-month value below and add the day of the month minus 1. September 13, 2027 is 244 + 12 = day 256.
| Month | Day number of the 1st (common year, e.g. 2027) | Day number of the 1st (leap year, e.g. 2028) |
|---|---|---|
| January | 1 | 1 |
| February | 32 | 32 |
| March | 60 | 61 |
| April | 91 | 92 |
| May | 121 | 122 |
| June | 152 | 153 |
| July | 182 | 183 |
| August | 213 | 214 |
| September | 244 | 245 |
| October | 274 | 275 |
| November | 305 | 306 |
| December | 335 | 336 |
To go the other way, find the largest first-of-month value that isn’t bigger than your number, then count forward. Day 200 in 2027: July starts at 182, and 200 − 182 = 18, so it’s July 1 + 18 days = Monday, July 19, 2027. In 2028 day 200 is Tuesday, July 18. Our leap years guide explains which years get the extra day.
Ordinal “Julian” dates: YYDDD and YYYYDDD
A date written as a year plus a day number is an ordinal date. The ISO 8601 standard defines it as a four-digit year and a three-digit day number, written 2027105 or 2027-105 for April 15, 2027, with day 1 written as 001.
In manufacturing and older business computer systems the same idea often goes by the name “Julian date”, usually in a shorter form:
| Date | YYDDD | YYYYDDD | YYYY-DDD |
|---|---|---|---|
| Friday, January 1, 2027 | 27001 | 2027001 | 2027-001 |
| Thursday, April 15, 2027 | 27105 | 2027105 | 2027-105 |
| Friday, December 31, 2027 | 27365 | 2027365 | 2027-365 |
| Tuesday, February 29, 2028 | 28060 | 2028060 | 2028-060 |
| Sunday, December 31, 2028 | 28366 | 2028366 | 2028-366 |
IBM’s documentation for its IBM i systems, for example, lists a “Julian” date format written as a two-digit year and a three-digit day, such as 96/015. Similar year-and-day codes are common on product packaging, and the term is also used this way in some military and logistics settings. Formats vary between makers (some use a single year digit, some add a plant or shift code), so if a code matters, such as an expiry or recall check, confirm how that manufacturer writes it.
Not the same as the astronomical Julian Day
Astronomers use “Julian Date” for something else entirely. NIST describes the Julian Day as a count of days from a starting point at noon on January 1, 4713 B.C., so its values run into the millions and don’t reset each year. It’s used to do arithmetic across centuries and calendars, and a related Modified Julian Date starts at midnight on November 17, 1858. See NIST’s time and frequency glossary for both definitions.
Neither has anything to do with the Julian calendar either, the older calendar that the Gregorian calendar replaced. When someone says “Julian date” on a production line or in a data file, they almost always mean the day of the year.
Days left in the year
Once you know the day number, the days left after today are 365 minus that number, or 366 minus it in a leap year. October 31, 2027 is day 304, so 365 − 304 = 61 days remain in 2027 after it. The days left in the year counter does this live and also gives the weeks, months and working days remaining, and days left until the end of 2027 counts ahead to next year.
Two landmarks are worth remembering: day 183 is the halfway point, July 2 in a common year and July 1 in a leap year, and day 365 is December 30 in a leap year rather than New Year’s Eve.
Day of the year in Excel and Google Sheets
With a date in cell A1, =A1-DATE(YEAR(A1),1,1)+1 returns its day of the year. Replace A1 with TODAY() for today’s number. To build a YYDDD code, use =TEXT(A1,"yy")&TEXT(A1-DATE(YEAR(A1),1,0),"000"). Day numbers and week numbers are different things: for weeks, the week number tool and the ISO week numbers guide explain how week 1 is defined.
Frequently asked questions
What day of the year is it today?
The answer changes daily, so check the year progress tracker, which shows today’s day number, the percentage of the year done and the days left.
What is day 100 of the year?
April 10 in a common year such as 2027, and April 9 in a leap year such as 2028.
What is a Julian date on food packaging?
Usually a year-and-day code such as 27105, meaning the 105th day of 2027, April 15. Formats vary between manufacturers, so check theirs if the date matters.
How many days are in a year?
365 in a common year and 366 in a leap year. 2026 and 2027 have 365 days; 2028 has 366.
Is the day of the year the same as the week number?
No. The day number runs from 1 to 366, while week numbers run from 1 to 52 or 53 and follow their own rules for where week 1 starts.