Work-Planning: end-date should be affected by start-date

When entering start-date and end-date in activities the end-date is not affected by the start-date.
Example:
clicking in the input field for start-date will bring up calendar with focus on today
set date in future for start-date
clicking in the input field for end-date will bring up calendar with focus on today

I would prefer if focus for end-date would be the previous selected start-date.
THX for thinking about.