The ones from before 1923 go public domain in less than 100 hours. The ones from 1923 go public domain in 2 years and 100 hours (there's an extra 1 year gap),

The ones from before 1923 go public domain in less than 100 hours. The ones from 1923 go public domain in 2 years and 100 hours (there's an extra 1 year gap), then it's one year per year until you reach 1946, which has a 10 year gap.