No action shall be brought after the expiration of one year from March 14, 1923, to set aside any decree or judgment entered in any action brought against unknown parties where there has been a substantial compliance with the requirements of the Colorado rules of civil procedure as to jurisdiction, pleadings, and service of process.
C.R.S. § 38-41-115
For service of process on unknown parties, see C.R.C.P. 4(g).