(concurring in result).
[¶ 16.] I concur in this result, even though unpaid support payments become judgments by operation of law and are enforceable, with interest from the date of each judgment. SDCL 25-7-7.4. Therefore, the monthly support, less the offset for the increase in the social security payment, plus interest on the balance, are due monthly. All other past due support payments are not subject to modification except “from the date that notice of hearing of the petition [for modification] has been given[J” SDCL 25-7-7.3.