Result of difference between two dates populated in a column

[China Diapers]

I have added two custom columns to Calibre, 'Start' and 'Finish', both hold date values. I want to calculate the number of days difference between these two date values and populate this in a third column.

Is this possible?

[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.

[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.

Many thanks, I shall take a look.

[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?

[China Diapers]

If I populate the template field with an example from the manual, e.g. :

{author_sort}/{title}/{title} - {authors}

It works, but not my days_between example.

[BetterRed]

@China Diapers - a search in MR for days_between found me this ==>> https://www.mobileread.com/forums/sh...15&postcount=6

BR

[China Diapers]

Originally Posted by BetterRed

@China Diapers - a search in MR for days_between found me this ==>> https://www.mobileread.com/forums/sh...15&postcount=6

BR

Thank you. Strange that worked for them, rather counter-intuitive. I enter:

days_between(field('#start_date'),field('#end_date '));

and in the result column I see the template expression rather than calculated result:

days_between(field('#start_date'),field('#end_date'));

[BetterRed]

See Using general program mode

program:
    days_between(field('#start_date'),field('#end_date'));

BR

[China Diapers]

Originally Posted by BetterRed

See Using general program mode

program:
    days_between(field('#start_date'),field('#end_date'));

BR

Thank you very much!

I have returned to using calibre after a few years, had no idea how powerful it is.