I need to be able to calculate the number of months someone has been a member, for each year. The trouble I’m having is that I want the same formula for each year, whether it’s the current year, or a past year–this way I can simplify it going forward. I have tried IF, IFS, IF(AND, and I cannot figure it out.

Here is the link to the data: https://docs.google.com/spreadsheets/d/1hyBfQBYF1TNmVgXammI5vADWFCD2d1eA/edit?usp=sharing&ouid=105919111240161574477&rtpof=true&sd=true

If you notice, I have a ‘Donations Summary 2023’ and a ‘Donations Summary 2024’, and column K shows the number of months for a member for 2023 and 2024 respectively. How do I calculate the number of months they’ve been a member–whether it’s partial year or entire year and whether they joined in the current year or previous year?