This is a good question. Unfortunately, this general topic is asked every week, making searching difficult. However, and if you look back maybe 6 months or a year ago you may be able to find some discussion of the Easter Vigil in the first half of the 20th Century. Someone stated that the vigil mass took place on Saturday morning. I don’t think there was any possibility of counting that as your Sunday obligation. I’m also not sure whether it really qualified as Sunday beginning Saturday, or if Easter Vigil was considered its own separate feast.
Anyway, the Liturgy of the Hours often fills in the gaps and clarifies what is occurring liturgically, so consulting an old copy of that should illuminate the issue of whether Saturday evening was liturgically Sunday, even if canonically it was not permitted to fulfill ones mass obligation on Saturday evening. I think the early 1960s date was when Saturday evening masses could first be routinely offered. However, I think that permission suggested that the masses were for those who were unable to attend on Sunday. In other words, people were “supposed” to attend on Sunday if they could rather than Saturday. That changed with the 1983 CIC, or possibly sooner.