Comment 18 for bug 1239127

Funny, you'd think he would remember doing this. Taken from the changelog he wrote:

    Remove from zone.tab the names America/Montreal, America/Shiprock,
    and Antarctica/South_Pole, as they are equivalent to existing
    same-country-code zones for post-1970 time stamps. The data entries for
    these names are unchanged, so the names continue to work as before.

The time zone is still valid which is why those commands work, but Montreal was removed from zone.tab, which defines where on earth ( longitude and latitude ) those zones are. This is why it is no longer an option.