You shouldn't change the presence column, because you need those fields to write times into the database (needed for history for example, because if you change it, you will always get 'created 44 years ago', because no 'Created Time' would be written into the database).
Instead, change the displaytype column to 4. This way the Time columns won't be shown, while dates will still be written into the database tables. (You can google for an explanation of all displaytype options - there are 4 options.)