2014-02-01 : Dawn to Dusk won’t affect any target that is illegal when it tries to resolve. If you chose to use both modes and both targets are illegal at that time, Dawn to Dusk won’t resolve.

2014-02-01 : You choose which mode you’re using—or that you’re using both modes—as you’re casting the spell. Once this choice is made, it can’t be changed later while the spell is on the stack.