Manage Events / search by date range uses incorrect WHERE criteria

When I go to "Manage Events" and use the "Find Events" box to search by date range, although it does narrow down the list, the search excludes some events that do overlap the search period, and includes some events that do not overlap the search period. The inclusion of incorrect events, occurs particularly when the event has a start date but no end date.

Screenshots are attached of the issue on our live site (4.4.20), 4.7 demo, and 4.6 on my personal test server.