"Separate property" means:
(1) Property acquired by a person before marriage;
(2) Property acquired by a person during marriage in exchange for separate property which was acquired before the marriage;
(3) Property acquired by a person during marriage, but excluded from treatment as marital property by a valid agreement of the parties entered into before or during the marriage;
(4) Property acquired by a party during marriage by gift, bequest, devise, descent or distribution;
(5) Property acquired by a party during a marriage but after the separation of the parties and before ordering an annulment, divorce or separate maintenance; or
(6) Any increase in the value of separate property as defined in subdivision (1), (2), (3), (4) or (5) of this section which is due to inflation or to a change in market value resulting from conditions outside the control of the parties.