score:2
The answers are, respectively, June 11, 1968 and July 1, 1967.
The source for my answer for Delaware is this Supreme Court of Delaware decision.
For Nevada, the present law is that the default effective date is October 1 (NRSβ218D.330.).
However, as the legislative history of that law states, it was amended in 1925, 1989, and 2011. The 1989 amendment changed the default effective date from July 1 to October 1. Thus, the default effective date of Nevada laws between 1926 and 1988 would have been July 1.
For these answers I must credit Comintern's comment for the initial clues.