Please Note: This article is written for users of the following Microsoft Excel versions: 2007, 2010, and 2013. If you are using an earlier version (Excel 2003 or earlier), this tip may not work for you. For a version of this tip written specifically for earlier versions of Excel, click here: Calculating the Day of the Year.
You've probably seen it on calendars before—some include an indication that "Today is the 123 day of the year with 242 remaining." You can easily calculate the day number of a year, as well as how many are remaining. For instance, let's assume you have a date in cell D27. You could use the following formulas to calculate, respectively, what day of the year it is and how many are still left:
=D27-"12/31/2012" ="12/31/2013"-D27
The reason that the first formula uses a date of 12/31/2012 is so the result will show the actual day number. Using these formulas, the result of 1/1/2013 in cell D27 would result in 1, meaning it is the first day of the year. (This is as it should be.)
Of course, once you enter the formulas, you need to format the cells as regular numbers. (Excel will, by default, try to format the cells as dates.) With the two cells selected, follow these steps:
Figure 1. The Number tab of the Format Cells dialog box.
ExcelTips is your source for cost-effective Microsoft Excel training. This tip (8727) applies to Microsoft Excel 2007, 2010, and 2013. You can find a version of this tip for the older menu interface of Excel here: Calculating the Day of the Year.
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2016-04-15 13:05:07
John
Given any date (any year) in cell A1,
=A1-DATEVALUE("1/1/"&YEAR(A1))+1 gives the day of the year.
=DATEVALUE("12/31/"&YEAR(A1))-A1 gives the number of days remaining in that year.
Regarding Brent's question, mm/dd/yyyy cannot be determined given only the day of the year; the year must also be specified. If the day of the year is in cell A1 and the year is in cell B1, then
=DATEVALUE("1/1/"&B1)+A1-1 gives the date (which can be formatted as mm/dd/yyyy)
2016-04-15 10:14:36
Dean
This is good. I use this as part of my Purchase Order number. Great reference.
2016-04-15 09:36:36
Brent Nielsen
What if you have the day of the year but wanted it in month/day/year format, is there an easy formula to provide this result?
PS I like the suggested comments.
2016-04-15 09:26:08
David Briggs
Alternatively, you could use the DATEDIF Function
Day of the Year
=DATEDIF( DATE(YEAR(TODAY()),1,0), TODAY(), "d" )
Days Left
=DATEDIF(TODAY(),DATE(YEAR(TODAY()),12,31),"d")
2016-04-15 07:14:08
Tony
to generalise for any dates, derive the start/end of year using the YEAR of the source date.
So assuming the date is in A2.
day of year=A2-DATE(YEAR(A2)-1,12,31)
days remaining=DATE(YEAR(A2),12,31)-A2
or =DATE(YEAR(A2)+1,1,1)-A2
depending if you want to include the current day or not.
2013-06-03 08:16:18
Bryan
Huh, for some reason I never knew you could use string literals for dates. Guess I just assumed it wouldn't work so I never tried it. Good tip.
If you want to generalize the formula a bit you could use =TODAY()-DATE(YEAR(TODAY())-1,12,31) to give you the current number of days into the year you are or =DATE(YEAR(TODAY()),12,31)-TODAY() for the number of days remaining (replace the both TODAY()'s with a cell reference to get the number of days into that year for that date).
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Please Note:
This article is written for users of the following Microsoft Excel versions: 2007, 2010, and 2013. If you are using an earlier version (Excel 2003 or earlier), this tip may not work for you. For a version of this tip written specifically for earlier versions of Excel, click here: 
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