Life + 70 has always been an oversimplification, we still haven't even reached 70 years since the introduction of these rules (1973 in the US, in other countries depends on when the US strogarmed them into adopting similar rules).

There's all sorts of quirks for anything published before that rule got standardised more-or-less worldwide, but in general 1930-1945 is still like a legal grey area that can be challenged in court and you should be good to go for anything published before that. And don't get me even started on posthumous publications, that's a whole different can of worms where a family member might claim some contribution (like for example Anne Frank's father), pushing the copyright further to the life of the author + life of that family member + 70.

Do you really think that the whole world is waiting for whatever the US say to make their laws? Spain copyright law is dated 1879: https://www.boe.es/buscar/doc.php?id=BOE-A-1879-40001 , based on the French _droit d'auteur_ laws of 1700's. About the matter being discused here, read Artículo 6: dead date + 80.