The state-mandated education day, established in 2009, is celebrated on May 22.
Milk, elected in 1977 to the San Francisco Board of Supervisors, was the first openly gay man elected to public office. Milk and Mayor George Moscone were assassinated in 1978.
The ads by "Save California" will not air in the Bay Area.
The Sacramento Bee reports they were purchased in Los Angeles and Sacramento.
The gay rights group "Equality California" says the campaign is "homophobic" and "encourages discrimination."