Since 2008, the interval arithmetic community has undertaken a collective effort to standardize this arithmetic. First, the need for such an effort will be demonstrated, along with the main principles underlying every decision. A schematic view of subjects handled so far and of decisions made until now will also be given. The matter of most debates was the mathematical definition of intervals and of operations upon them, be they arithmetic operations or operations upon sets. In particular, handling of exceptions such as square root of the interval [-1,2] has been the subject of many lively discussions. Finally, consequences of these discussions at the implementation level are also developed.