History / etymology of the French word aujourd'hui (today)

From Auxlang, courtesy of Jens Wilkinson:

Actually, this reminds me of a great book that I recently read, called The Unfolding of Language. The author discusses how languages are both destructive and constructive at the same time, so there are always processes processes of shortening and lengthening going on at the same time. One example he uses is how in French, a lot of words are shortened from Latin. But there is really interesting word,"aujourd'hui" (today). The "dui" originally comes from Latin hoc die, meaning "this day". So the whole word means literally "on the day of this day." Presumably "dui" became too short in a way. According to the author (and maybe Olivier knows if this is true or not), some French people even say "au jour d'aujourd'hui".