C.R.S. § 1-40-108

(1) No petition for any ballot issue is of any effect unless filed with the secretary of state within six months from the date that the titles and submission clause have been fixed and determined pursuant to the provisions of sections 1-40-106 and 1-40-107 and unless filed with the secretary of state no later than three months before the election at which it is to be voted upon. A petition for a ballot issue for the election to be held in November of odd-numbered years must be filed with the secretary of state no later than three months before such odd-year election. All filings under this section must be made by the close of business on the day of filing. (2)(Deleted by amendment, L. 95, p. 433, § 6, effective May 8, 1995.)