Cannot update datetime in text field after selection in calendar

Description

Note: This issue doesn't happen in Release 7.5.

Steps to reproduce

1. Create a new page.
2. Select Schedule for Publish in the Publish menu.
3. Open the DateTime picker.
4. Select a Date only.
5. Click outside to close the DateTime picker.
6. Edit the time value on the "Publish on" textbox with a valid data.
7. Click outside.

Expected: The Time value is kept.
Actual: The Time value reverts to the default (12:00 PM).