Action card date sync will allow subaction due dates to 'roll up' to the parent card. By default these two date fields are unlinked, but you can turn on this date sync in project settings.

In order to change this setting in a project, navigate to More > Edit Project > Advanced settings > Action card settings

With this setting turned on, the start and end date of your action card(s) will automatically be updated as your subactions' dates change.