User can schedule "Clone Issue" action for issue create date or issue due date by choosing proper "repeat by" option. There is also field where issue duration could be set in days.

When set-up new repating for issue add-on will calculate and set issue duration field based on original issue as working days between original issue create date and original issue due date. If original issue has not due date then issue duration field will have value equal 0. User can always change this value to other before save the repeating. 

If issue duration will not be provided in repeating set-up screen and the original issue has valid due date then when new cloned issue will have duration calculated from original issue.

Versions up to 0.6.2

The cloned issue due date is adjusted to reflect the new occurrence's dates and it is calculated on original issue created date and due date with following algorithm:

clonedIssue.dueDate = clonedIssue.createdDate + Duration.between(originalIssue.createdDate, originalIssue.dueDate)

Assume the original issue created date is 2016-11-07 and due date is 2016-11-18. If new cloned issue falls on date 2016-12-01 (it is created date) then its due date will be set to 2016-12-12.

Please note that both original issue created date and due date must be provided to set cloned issue due date when cloning.