I was watching the newest Always Open (#134) and Barbara Dunkelman asked the question, "What is the actual difference between something-zero and something-diet? I don't know what it is?"  This prompted me to finally join as I had just looked up the difference myself not too long ago. Diet Coke was launched in 1982 with a Coke formula that was based on the TAB formula, the premier diet soda from coke at the time. Diet Coke took off in popularity this prompted Coke to make New Coke in 1985 by adding high fructose corn syrup to the formula.  Where Diet Coke was a huge success New Coke was a disaster and Coke Classic was introduced within a few months with the original Coke formula  Coke Zero was introduced as a diet soda with a formula much closer to the original Coke (Coke Classic)