There are 2 related issues when a user saves task forms with a date field.
1. Enter text in the date field , and click save or complete in the task details page it is not checking the date format (does not raise an error) and task is then saved/completed with wrong data (the current date).
2 . When we have a date value in a date filed (a human task form with input data that has this date set), now remove the value from date field in the form , and click save from task details page, if you reopen the task details page of the same task again the task value is not getting removed, it stills retain the old value.