After importing a csv file, you could not be able to sort your data, if you have to sort “date” cells. Indeed, even setting cells as date format and the right date format (such as GG/MM/AAAA or the like), you couldn’t be able to sort as expected your data.
To fix this, as explained here, you should import in LibreCalc a csv file with something like “date” checking “Detect special numbers” field. In this way you should be able to sort your items by the “date” columns.