Day/Night Cycle Broken

Whenever I load up a new world in this snapshot, the Day/Night Cycle is broken. It's as if doDaylightCycle is set to False by default.

The sun goes up a little bit then just goes straight back down again to where it was a few seconds later, as if the time was being set to 0, but it does this endlessly.

EDIT: This glitch also seems to affect mobs. They move in slow-mo when this is happening.