(a) A durable power of attorney for health care executed after July 1, 1991, is effective to authorize the attorney in fact to make health care decisions for the principal only if the power of attorney complies with this part.
(b) A durable power of attorney for health care executed after April 8, 1990, and before July 1, 1991, is effective to authorize the attorney in fact to make health care decisions for the principal if the power of attorney was executed in compliance with this part as in effect on that date.
(c) A durable power of attorney executed before April 9, 1990, that specifically authorizes the attorney in fact to make decisions relating to the medical or health care of the principal is deemed to be valid under this part, notwithstanding that it fails to comply with all of the requirements of this part.
(d) Nothing in this part affects the validity of a decision made under a durable power of attorney before April 9, 1990.
(e) Any durable power of attorney for health care properly executed before May 5, 1995, shall be enforceable notwithstanding any failure to notarize signatures of witnesses to the instrument.