Holidays. Columbine day June 18 set aside. Post June 7, 1925 p.13 sec.l June 18, 1926 celebration. To be observed June 9D M F 9#5-7 May-July, 1926 p.17 . denver municipal facts RMN May 29, 1927 P.7 sec.l Governor Johnson proclaims June 18 as Columbine Day. Post June 15, 1936 p.11 Suggestion that there should be a Colorado Columbine day. Times June 1, 1900 p.6 c.5