Avoda Zara 25 cites a difference of opinion as to how long the sun stood still for Y'hoshua: twelve hours, twenty-four, or thirty-six. According to those who say twelve or thirty-six, the sun finally set at a time (on watches, if you will, or hourglasses) that was twelve hours after the hourglasses indicated "sunset". And the next time the hourglasses indicated "sunset", it was astronomical morning, around sunrise or so. Likewise for every subsequent day, until now: any hourglass or watch that has been set in place since the time of Y'hoshua and not adjusted since would indicate "sunset" every morning. Yet we indicate the start of a new calendar date at sunset, not in the morning. Thus, dates start not when the sun "should" set but when it does: a new date does not start until the sun actually sets, even if (as in Y'hoshua's case) it "should" set earlier than that.
Now, Sifse Chachamim to Noach 8:22 says that, for the duration of the mabul (deluge), the sun and other orbs stood still, not moving in the sky: they remained, for the whole mabul, wherever they were at the start of the mabul, and there was no sunset. According to the paragraph above, then, the date should not have changed throughout the mabul. Yet the p'sukim (e.g., 8:4–5) clearly refer to the passage of dates. What's going on?
(This is a question on the Sifse Chachamim. The R'em, for example, has a wholly different explanation of what occurred during the mabul.)