How to set up a lastUpdatedAt cell in Google Sheets (#snippet)

I tried many habit trackers over all these years. Nothing stuck for longer than a few months. For now, it looks like I'll be sticking with a good old Google Sheet.

While setting up a new sheet for 2021, I was looking for a quick way to display lastModifiedAt/lastUpdatedAt in a sheet row. When I update a value in a row, the idea is that the row also includes the update day information.

I found a beautiful solution in a StackExchange thread.

Many people in the thread advised to set up a complicated formula or function, but one solution stood out because of its simplicity.

=iferror(A1+B1+C1+"x",today())

You can set the above Excel formula to a cell. This formula tries to sum up all the depending cells (you have to define these) with the value x, and if that throws an error (which it always does), it sets the cell value to today.

Let's go over this formula step by step:

• whenever you update a dependency (A1, B1 and C1), the cell defining the above formula reacts and is updated as well
• the calculation adds the value x to the other cell values and throws an error
• the iferror function catches the error and defines the cell value as today

While this solution might feel hacky, I have to say that I like its simplicity a lot.