The rules say "If the Sun Event deck is depleted, shuffle the discards
and form a new deck", which I read as meaning that you shuffle as soon
as you draw the last card. Is this the intention?
It matters if the last card is drawn from the deck at the end of the
last Sun phase before a Sapa Inca phase. If you reshuffle right away
you get the discards that are there at that time, but if you wait until
you need to draw a card you'll shuffle in the cards discarded during
I believe this happened during our (first) game last night. If my
figuring is correct in a 4 player game this will happen before the
first scoring of the middle empire.
We've always played not to reshuffle until you need a card and one was not available. This shouldn't really matter though as all the cards played during a Sun phase stay in play until the entire turn is over. If you are in the middle of a turn with multiple Sun phases and you need to reshuffle, cards previously played this turn are still in play until the end of the turn and therefore not on the discard pile to be reshuffled.