Technically, Saturday evening is already Sunday. Sundays and Solemnities begin with Evening Prayer I on the evening of the previous day.But it’s technically not the Sabbath. This is in violation of the law. How does the church reconcile this?
That’s why it’s not correct to say that Saturday evening Mass should be used only out of necessity. Actually, attending Saturday evening Mass for any reason, even out of preference, is good enough because it is already Sunday.