Hi folks - I get what the message is saying... but struggling to understand how to fix this in an Anaytics Workbook, any ideas? They are both TO_CHAR and 'MM' format from the date.

you are subtracting chars

Interesting and logical, it's odd since this formula worked in a Saved Search. I'll give it a shot, thanks.

honestly, you can also use the dates for subtraction too

Tried the originally and it didn't work out the way you'd think and misses the purpose of the search that was bui.t

the difference between two dates is a float which represents a difference in days