[China Diapers]

Originally Posted by DaltonST

Yes, if you create a template function to do so.

See: https://manual.calibre-ebook.com/template_lang.html

Create a custom composite column to test templates. Once you have the column, you can change its template simply by double-clicking on the column.

I have been experimenting with this and something strange is happening. I have created a column with type 'Column built from other columns' and tried entering the below in the template field:

days_between({#start_date},{#end_date}) returns "days_between(,)"
days_between(#start_date,#end_date) returns "days_between(#start_date,#end_date)"

What am I doing wrong?