Zone America/Edmonton has
Rule    Edm     1967    only    -       Apr     lastSun 2:00    1:00    D
Rule    Edm     1967    only    -       Oct     lastSun 2:00    0       S

This is wrong. There was no DST in Alberta in 1967.

see article in Calgary Herald, 29 April 1967

My other source (a professional user of astro.com) also claims that there was no DST in 1969. I have not yet verified this from newspaper archives.