Prep day shorter then real time.
I started upgradng my level five archer tower to level 6, which takes twentyfour hours. Then I waited a few minutes and started a war search. By the time I found one, the archer tower had 23 hours 58 minutes left, and prep day had 23 hours 59 minutes left. I went to sleep. Now, the archer tower has 8 hours 15 minutes, and prep day has 8 hours 7 minutes left. It's not fair that now I will have to pay gems to finish the tower because supercell messed up their timer. I did some timing and a prep day minute is actually a full second faster than the upgrade time. Doesn't seem like much? Every hour prep day will be one more minute ahead, so after twentyfour hours, it will be twenty four minutes ahead. That's 8 gems I'm paying because supercell messed up.