are generally presumed to operate prospectively. Section 2-4-202, C.R.S. (1980 Repl.Vol. IB). Thus, we conclude that the statutory prohibition against dual valuation challenges enacted by the 1990 amendments to § 39-10-114(l)(a)(I) was applicable only to property tax years beginning in 1990 and thereafter. Consequently, when the General Assembly again amended § 39-10-114(l)(a)(I) in 1991 and in so doing expressly provided that the statutory prohibition against dual valuation challenges applied only to' property tax years beginning in 1990 and thereafter, the 1991 amendments merely clarified the status of already existing law as to the applicability of this statutory prohibition. See Colo.Sess.Laws 1991, ch. 309 at 1962-65; see also Portofino Corp. v. Board of Assessment Appeals, supra (<HOLDING>). Under these circumstances, we conclude that
holding that the protect act amendments to the standard of review apply retroactively holding that the  1981 amendments contained in  101 of the civil rights act of 1991 do not apply retroactively holding that the aedpa oneyear statute of limitations applies to amendments to  2255 motions holding that the 1991 mixedmotive amendments do not apply to  1981 based on an independent analysis of the amendments and  1981 holding that 1991 amendments to other aspects of  3910114lai clarified intent of 1988 amendments to statute