How to Use the DAY function in Excel
The syntax for the DAY function is DAY(serial_number). The only argument for the DAY function is serial_number, which is required. This serial number field refers to the date of the day you are trying to find. Dates are serial numbers in Excel’s internal system. Beginning with January 1, 1900 (which is number 1), each serial number is assigned in ascending numerical order. For example, January 1, 2008 is serial number 39448 because it is 39447 days after January 1, 1900. Excel uses the serial number entered to determine which day of the month the date falls on. The day is returned as an integer ranging from 1 to 31.
DAY Function Not Working
If your results are not appearing as numbers but rather as dates, it is likely a simple formatting issue. Problems could occur if the numbers are formatted as text rather than dates. Checking the format for the cells containing the serial number portion of the DAY function syntax (and then changing the format, if necessary) is the most likely way to resolve an error or incorrect result.
When to Use the DAY Function in Excel
The DAY function is useful for financial analysis, primarily in a business setting. For instance, a retail organization might want to determine what day of the month has the highest number of customers or when most shipments arrive. You can also extract a value using the DAY function inside of a larger formula. For instance, in this sample worksheet, the DAY function helps determine how many days are in the listed months. The formula entered in cell G3 is The DAY function provides the day component and EOMONTH (end of month) gives you the last day of the month for that date. The syntax for EOMONTH is EOMONTH(start_date, months). So the start date argument is the DAY entry and the number of months is 0, resulting in a list showing the number of days in the months presented.
