Sections 325G.29 to 325G.34 and 325G.36 take effect on July 1, 1983. Section 325G.35 takes effect May 29, 1981. Sections 325G.29 to 325G.36 do not affect any consumer contract executed before July 1, 1983. A previously existing consumer contract renewed after July 1, 1983, is subject to sections 325G.29 to 325G.36. No provision for renewal of a consumer contract is invalid merely because compliance with sections 325G.29 to 325G.36 changes the form of the renewal agreement. For the purposes of this section periodic tenancies renew at the commencement of each rental period.