Google Sheets – How to Add or Subtract Quarters Using Formulas

Using mid() extract the quarter portion of the original date, here after referred to as Q. Similarly extract the year portion, here after referred to as Y. The amount to be added will be referred to as D.

To get the new quarter add D to Q and modulo by 4. This will be correct except it will equal 0 when it should be 4. Wrap this whole portion in an if() to handle that case and we are done.

Moving on to the new year. Add Y to the trunc() of (Q+D)/4

When Q+D is negative or a positive multiple of 4 we end up 1 to high. Add a check for that at the end.

Take these two values and concatenate them with a Q in-between

=if(mod(MID(E15,1,1)+F15,4)=0,4,mod(MID(E15,1,1)+F15,4))
&"Q"&mid(E15,3,4)+trunc((MID(E15,1,1)+F15)/4)+
if(or(mod(MID(E15,1,1)+F15,4)=0,MID(E15,1,1)+F15<0),-1,0)

Original date is in E15 and the number of quarters to be added to it in F15

This answer is not Y2K compliant, but that's on you and your 2 digit years, if you go to 4 digit you will need to change the mid() for the year to be mid(3,6)

MID

TRUNC

MOD