**As** a user
**I want to** have a consistent and understandable inheritance of dates (start/finish) up and down the work package ancestor chain 
**so that** I know what is going to happen when I alter the work package hierarchy (e.g. add a child/parent)

**Acceptance criteria**

* Inheritance of dates Begin of the deletion (finish/start)End of the deletion up the ancestor chain Begin of the insertion(from child to parent)End of the insertion should always only be for the date that is set. Begin of the insertionE.g: End of the insertion Begin of the deletion E.g:End of the deletion
* Begin of the insertionIf neitherEnd of the insertion Begin of the deletion When setting a start date on a child and bothEnd of the deletion the parent Begin of the insertionnorEnd of the insertion Begin of the deletion as well asEnd of the deletion the child Begin of the insertionhasEnd of the insertion Begin of the deletion did not haveEnd of the deletion any dates Begin of the insertionset:
* Setting aEnd of the insertion Begin of the deletion left, only theEnd of the deletion start date Begin of the insertionon a child will mean that thatEnd of the insertion Begin of the deletion of theEnd of the deletion parent Begin of the insertionwill inhert _only_End of the insertion Begin of the deletion is to be set toEnd of the deletion the Begin of the insertionstartEnd of the insertion Begin of the deletion sameEnd of the deletion date Begin of the insertionfromEnd of the insertion Begin of the deletion asEnd of the deletion the child's start date. Begin of the insertionFinish date and duration (if present) remain unchanged.
* The same is true forEnd of the insertion Begin of the deletion BothEnd of the deletion finish Begin of the insertiondate; when the child only has a finish date, the parent can only inherit this finish date, and startEnd of the insertion date and duration Begin of the insertion(if present) remainEnd of the insertion Begin of the deletion are to beEnd of the deletion unchanged.
* Inheritance of dates (finish/start) down the ancestor chain Begin of the insertion(from parent to child)End of the insertion should always only be for the Begin of the insertiondatesEnd of the insertion Begin of the deletion dateEnd of the deletion that Begin of the insertionare set. End of the insertion Begin of the deletion is set. E.g:End of the deletion
* Begin of the insertionSo when the parent has start _and_ finish dates:
* A newEnd of the insertion Begin of the deletion When creating aEnd of the deletion child (regardless of whether it is the first or a subsequent Begin of the insertionone createdEnd of the insertion Begin of the deletion one)End of the deletion via any Begin of the insertionmeans) inherits both ofEnd of the insertion Begin of the deletion means, andEnd of the deletion the Begin of the insertiondates (and naturally also the duration).
* When theEnd of the insertion parent Begin of the insertiononlyEnd of the insertion has Begin of the insertiononeEnd of the insertion Begin of the deletion a startEnd of the deletion date Begin of the insertion(start _or_ finish):
* A newEnd of the insertion Begin of the deletion and a finish date set, theEnd of the deletion child Begin of the insertion(regardlessEnd of the insertion Begin of the deletion is to receive bothEnd of the deletion of Begin of the insertionwhether it isEnd of the insertion the Begin of the insertionfirst or a subsequent one created via any means) inherits _only_ this date;End of the insertion Begin of the deletion dates (andEnd of the deletion the Begin of the insertionother date and duration remain unchanged.End of the insertion Begin of the deletion duration)End of the deletion
* Begin of the deletion TBD:End of the deletion If Begin of the insertionan existingEnd of the insertion Begin of the deletion aEnd of the deletion work package is turned into a child, the Begin of the deletion newEnd of the deletion parent Begin of the insertionwillEnd of the insertion Begin of the deletion shouldEnd of the deletion receive only the date Begin of the insertionor datesEnd of the insertion (start/finish) Begin of the insertionthat areEnd of the insertion set on the new Begin of the insertionchild. 
* It inheritsEnd of the insertion Begin of the deletion child. IfEnd of the deletion the Begin of the insertionstart date of the earlierEnd of the insertion child Begin of the insertionandEnd of the insertion Begin of the deletion already has dates set,End of the deletion the Begin of the insertionfinish dateEnd of the insertion Begin of the deletion minimumEnd of the deletion of the Begin of the insertionlatest child.
* If no child has aEnd of the insertion start Begin of the insertiondate, thenEnd of the insertion Begin of the deletion dates are used forEnd of the deletion the Begin of the insertionparent will have noEnd of the insertion Begin of the deletion parent'sEnd of the deletion start date Begin of the insertion(inheritingEnd of the insertion Begin of the deletion andEnd of the deletion the Begin of the insertionfinish dateEnd of the insertion Begin of the deletion maximumEnd of the deletion of the Begin of the insertionlatest child).
* If no child has aEnd of the insertion finish Begin of the insertiondate, thenEnd of the insertion Begin of the deletion dates are used forEnd of the deletion the Begin of the insertionparent will have noEnd of the insertion Begin of the deletion parent'sEnd of the deletion finish Begin of the insertiondate (inheriting the start date of the earliest child).End of the insertion Begin of the deletion date.End of the deletion
* Begin of the insertionWhen milestones become a child, their uniqueEnd of the insertion Begin of the deletion Open: How to handle the oneEnd of the deletion date Begin of the insertionwill be considered start and finish, andEnd of the insertion Begin of the deletion of milestones? IsEnd of the deletion it Begin of the insertionwill behaveEnd of the insertion Begin of the deletion bothEnd of the deletion the Begin of the insertionsameEnd of the insertion Begin of the deletion startEnd of the deletion as Begin of the insertiona one-day work package (withEnd of the insertion Begin of the deletion well asEnd of the deletion the Begin of the insertionsame start andEnd of the insertion finish Begin of the insertiondates).End of the insertion Begin of the deletion date?End of the deletion

#### _Current behaviour_

* Creating the first child from within the relations tab:
* If the parent has a start date and no date is provided for the child by the user: The child's start date is set to the parent's start date. The parent's finish date is set to the start date of the child (which is the same as the parent's start date) and the duration is set to 1.
* Creating the second, third, ... child from within the relation tab:
* If the parent has a start date and no date is provided for the child by the user: The child's start date is not set. No change is done on the parent's dates.
* Assigning a parent to an already existing child (e.g. via "Set parent" on the full/split screen or by indenting on the Gantt chart)
* The dates of the parent are overwritten. This includes parent dates being deleted in case the child does not have dates.