Bug: Advanced date filter is reset to a single month when selected for edit

Set the date range for Advanced search to e.g.

2016-5-15 => 2016-6-15

Press OK

Decide you want to change the range, select it

The range changes to

2016-5-1 => 2016-5-31

i.e. the month that includes the start date

That's really annoying.

P.S. it does not help that the date field is too narrow to show the date range

Reproduce the Advanced search date-range edit flow described in the issue, using a range such as 2016-5-15 to 2016-6-15. Trace the date-filter handling from selection through editing; done means reopening the filter preserves both original endpoints rather than replacing them with the start month.

Written by the indexing model from the issue text.