I'm not sure if this explains the different dates, but there is a difference between being "aligned with" the galactic plane and "crossing" that plane. One need not be aligned with a plane when crossing it, nor do you have to be crossing it to be aligned with it.

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Bring back Firefly!

"It is quite clear that Occam's razor does not sharpen in your pyramid." (Nicolas)

"Still, a man hears what he wants to hear and disregards the rest." (Paul Simon)