In the 1983 ( :barf: ) "Code of Canon Law" it says:
Can. 1248 §1. A person who assists at a Mass celebrated anywhere in a Catholic rite either on the feast day itself or in the evening of the preceding day satisfies the obligation of participating in the Mass.
But that does NOT say Sunday. In the previous canon, it mentions Sunday, but not this one.
Can. 1247 On Sundays and other holy days of obligation, the faithful are obliged to participate in the Mass. Moreover, they are to abstain from those works and affairs which hinder the worship to be rendered to God, the joy proper to the Lord’s day, or the suitable relaxation of mind and body.
I don't know where people are getting this from. It doesn't say anywhere that you can go on Saturday, and fulfill your Sunday obligation. And I saw on "Father Z's" website

where he said that it does...
Hilarious.
http://wdtprs.com/blog/2008/11/quaeritur-does-a-tlm-on-saturday-evening-fulfill-a-sunday-obligation/