Steps to reproduce the issue

1. Open the Article Edit screen, click the Publishing tab
2. Click the Start Publishing field and select any date
3. Click outside the field to close the calendar window
4. Click the Start Publishing field and manually change the value using the keyboard
5. Click outside the field to close the calendar window
6. Click the Start Publishing field again - the value revert to its previous (non-keyed) value

Expected result

Calendar field retains keyed in value

Actual result

Calendar field reverts to previous value (as stored in data-alt-value attribute on the text input)

System information (as much as possible)

Joomla 3.7
PHP 5.6

Additional comments

The values are retained if you hit 'enter' after making changes as per step 4, but not if you just click away. This differs from Joomla 3.6.X

See video of issue in action at http://support-media.muckypuddle.me/kUe5