"All day" checkbox is always checked by default, while there is another field "Estimated time".

Both fields should be correlated somehow. In my workflow I use the duration to schedule my day/week together with calendar (mac/google), and it is very annoying to have to edit task by task disabling the "All day" checkbox.

Please solve it by allowing to edit the default value of "All day" checkbox, and include estimated time into the task property when syncing with google calendar.