Day of the year: what day of the year is it today

How the day of the year is counted

The day of the year is the position of a date within its year. 1 January is day 1, 1 February is day 32 and 31 December is day 365, or 366 in a leap year. There is no day 0.

For 23 October 2026 the full result reads like this:

Going the other way, day 100 of 2026 is Friday 10 April, and day 256 is Sunday 13 September. The converter accepts any day number from 1 to the length of the chosen year.

Leap years change every number after February

A year is a leap year if it divides by 4, except century years, which must divide by 400. So 2028 is a leap year, 2100 is not, and 2000 was. Leap years add 29 February as day 60.

Days in January and February keep the same number in every year. From 1 March on, a leap year runs one higher: 1 March is day 60 in 2026 and day 61 in 2028, and 31 December is day 366 in 2028. If you compare day numbers across years, check whether either year is a leap year.

The ordinal date in ISO 8601

ISO 8601 calls a year plus a day of the year an ordinal date. The extended form is 2026-296 and the basic form, without the hyphen, is 2026296. The day always has three digits, so 1 February 2026 is 2026-032.

The same structure appears outside the standard under the name “Julian date”. A Julian date code such as 26296 is the two-digit year followed by the three-digit day, and 2026296 in YYYYDDD form is identical to the basic ISO ordinal date. The astronomical Julian Day is a different number altogether: a continuous count of days since 4713 BC, which is 2461337 for 23 October 2026.

Calculating the day of the year by hand

Add the lengths of all earlier months to the day of the month. For 23 October 2026, January to September hold 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 = 273 days, and 273 + 23 = 296.

To go back from a day number, subtract month lengths until the remainder fits in the next month. For day 100 of 2026, January to March hold 90 days, so 100 - 90 = 10 gives 10 April. The ISO 8601 page shows how the ordinal date fits next to the calendar and week forms.

Day of the year in Excel and code

In Excel and Google Sheets, with a date in A1:

=A1-DATE(YEAR(A1),1,0)

DATE(YEAR(A1),1,0) is day 0 of January, which Excel rolls back to 31 December of the previous year. Subtracting it leaves the day number. Format the result as a number, or Excel may show it as a date in 1900. For days left in the year, use =DATE(YEAR(A1),12,31)-A1.

To turn a day number back into a date, with the year in A1 and the day number in B1, use =DATE(A1,1,B1). DATE rolls large day values into later months, so DATE(2026,1,296) is 23 October 2026.

In code:

• Python: date(2026, 10, 23).timetuple().tm_yday returns 296, and date(2026, 1, 1) + timedelta(days=295) goes back.
• JavaScript: Math.round((Date.UTC(2026, 9, 23) - Date.UTC(2026, 0, 0)) / 86400000) returns 296. Months are zero-based, and using UTC avoids daylight saving errors.
• SQL: PostgreSQL has EXTRACT(DOY FROM date '2026-10-23') and MySQL has DAYOFYEAR('2026-10-23'), both returning 296.

Where day numbers are used

Day numbers appear wherever a short, sortable date is needed. Food lot codes and US egg cartons print the day of the year, and logistics and mainframe systems join it to the year as a Julian code. Project schedules and reports often state progress as “day 296 of 365”.

For a full table of every day in the year with its number, use the 2026 day of year calendar, which is the same list as the Julian date calendar. Week-based schedules are covered on the week number page.

Questions