Hmmm...interesting, wow. T.S. Eliot's quote, "Only through time time is conquered" seems to confirm the second.
But, then again, do we say "all through history" or "all throughout history," especially in speaking of geological time?
And then there's the song with the famous refrain, "All through the night." So why can we go "though" night, but must go "throughout" the day? But then if "through" is "out" it's not really "through," is it? So should we throw out the out from throughout?
Oh, yes, wow!...as you can see, it must be a rainy day! All through and throughout!