When we are asked “What is 90 days prior to today?” we need not fret.  Excel allows us to calculate the date 90 days before today by using TODAY function and subtraction.  

Figure 1.  Final result:  What is 90 days prior to today?

How to calculate the date 90 days prior to today

The formula to calculate the date 90 days ago is:

=TODAY()-90

Enter the formula in cell D4

=TODAY()-90

Figure 2.  Output: Calculate the date 90 days ago

The TODAY function returns the date today in the form of a serial number.  Then we subtract 90 from the serial number of the date today, which results to a serial number 90 days ago.  Excel automatically takes into consideration the number of days in a month, be it 30, 31 or even 28 (for February).  As a result, our formula returns “09-Feb-19”.

What day was 90 days ago

Now that we have determined the date 90 days prior to today, we might also wonder “What day was 90 days ago?” The same formula is used here, we only need to change the format of our cell to show the day name.  

  • Select the cell containing the date
  • Press Ctrl + 1 to launch the Format Cells dialog box
  • Select Custom under the Name tab
  • Select the type “dddd

Figure 3.  Custom format in Format Cells

As a result, we have applied the custom format to the date that shows the full name of the day on February 9, 2019, which is a Saturday.

Figure 4.  Output: Day name using custom format