Released at ComingSoon.net along with the film's title card, the official synopsis of Day & Night reads:
When Day, a sunny fellow, encounters Night, a stranger of distinctly darker moods, sparks fly! Day and Night are frightened and suspicious of each other at first, and quickly get off on the wrong foot. But as they discover each other's unique qualities--and come to realize that each of them offers a different window onto the same world--the friendship helps both to gain a new perspective.
A simple concept, with great comic potential. Exactly what's made previous Pixar shorts so enjoyable.
Day & Night is being directed by artist and character designer Teddy Newton. This is his directorial debut at Pixar. Studio veteran Kevin Reher is producing (he previously produced A Bug's Life and Partly Cloudy). Music will be by Michael Giacchino, a man who needs no introduction to Pixar fans. We'll be learning lots more about the short in the coming weeks, for sure, as June 18 rapidly approaches.
To point out the obvious, Day & Night (previously rumoured as "Night and Day") is not the boy/dinosaur project, as I previously theorized. Hmmm... This seriously raises the possibility that 'boy/dinosaur' is a feature in production, not a short at all. It could be Pete Docter's secret 2013/2014 feature project, with Greg Dykstra as co-director.
Update: We're already getting new details regarding Day & Night.
Up art director Don Shank writes on his blog Shank Pile: "I am very excited that the public will finally get to see it because it's unlike anything Pixar has produced before." Shank served as production designer on the short film; he calls his experience "one of the best times I’ve ever had working on anything".
Pixar Talk points to a comment posted on Cartoon Brew, written by the site's own Jerry Beck, animation historian, that claims that "the images “inside” the characters will be CG, but Day and Night is essentially a 2D short. The character animation is all hand drawn."
A reasonable theory, when you consider Shank's comment and the 2D title card that has raised so much speculation about whether the short will be traditionally animated. Makes sense. This should look awesome on screen in stereoscopic 3-D.
(Updated at 8:51 PM)