YES! And I'm in dire need of $1,000,000...
I sense you might not aware be there are two standard fields: 
rdate (
Release date) and 
release (currently not used by any plugins AFAIK). So from your description, it seems you're exporting 
rdate and re-importing as 
release. Remember, you won't see 
release unless there is a value in it, or you're in edit mode.
you cannot add the releasing date manually...
I'm not sure what you mean by this. You should be able to edit or import to either of these fields, like any other. 
Last modified can't be changed—it's a system value.