How do I define days during which the library is closed ?

If you want to prevent that the date of return of a book is a week-end or a holiday, define the days when the library is closed.

In the Maintenance, choose the Other>Configure the diary command.

Click on Add in order to define a new period.

You can for instance generate in one operation all week-ends in the year by typing as start date the 1st of January and as end date the 31st of December, then tick the Sa and Su checkboxes.