To calculate the day of the year in Excel, you will need to use a combination of the YEAR function and the DATE function. The YEAR function returns the year for a given date, while the DATE function returns the day of the year for a given date. By combining these two functions, you can calculate the day of the year for any date in Excel.

To use the YEAR function, you will need to enter the following into a cell:

=YEAR(date)

Replace date with a cell reference that contains a valid date. For example, if you have a date in cell A1, you would enter =YEAR(A1). This will return the year for the date in cell A1.

To use the DATE function, you will need to enter the following into a cell:

=DATE(year, month, day) 

Replace year, month, and day with values that correspond to a valid date. For example, if you want to calculate the day of the year for December 31st, 2016, you would enter =DATE(2016, 12, 31). This will return 365, which is the day of the year for December 31st.

You can also use the DATE function to return the day of the year for a given date. For example, if you have a date in cell A1, you would enter =DATE(A1). This will return the day of the year for the date in cell A1.