C.R.S. § 30-28-139
Section 2 of chapter 132, Session Laws of Colorado 2003, provides that provisions of this section addressing the requirements of notice and hearing only apply to mergers that take effect on or after October 1, 2003, and that provisions of this section addressing the assessment of merged parcels as one parcel of real property for purposes of the levying and collection of the tax on real and personal property apply to mergers that take effect prior to, on, and after October 1, 2003, but shall not be construed to require a reassessment of property for property tax years commencing prior to January 1, 2003.