Fulfilling one's Sunday obligation on a Saturday night because it's "Sunday" is ridiculous. If people really believed that, then they also shouldn't do any servile work after sundown on Saturday, go shopping on Saturday night, certainly not "hit the bars or casinos" on Saturday night, and should start abstaining from meat on Thursday evenings, since according to that reasoning it's really Friday by then.
There is a story about this very thinking from the life of St Notburga;
Next, Notburga worked for a peasant in Eben am Achensee
, on the condition that she be permitted to go to church evenings before Sundays and festivals. One evening her master urged her to continue working in the field. Throwing her sickle
into the air she supposedly said: "Let my sickle be judge between me and you," and the sickle remained suspended in the air. https://en.wikipedia.org/wiki/Saint_Notburga