It doesn't seem that conditional formatting is able to achieve what I'm trying to do. I'm looking for a way to make a range of cells to each auto-update its own border color based on the duration of when its data was last modified. The cell data is arbitrary, i.e. any number or text.
Border colors should indicate how long ago was the cell updated: yellow = less than 3 months ago, orange = less than 6 months ago, red = 6 months ago or more.
I'm not familiar with if Google Sheets keeps track of last modified per cell by default or offers version control information per cell.
If it comes to it, using cell Comment to keep track of last changes and timestamps would be alright, but preferably, I could just punch in numbers or text into a cell, instead of doing that and then also adding a comment to the cell.
Hope that makes sense.