If you had level 3 farming, and farmers to do the work, then the most likely reason I can think of is that the farmers got sick. They won't voluntarily work while sick, so if you had no doctor to heal them they never would have gotten back to work. And if it was off for a while (like overnight) the fire will go out, which makes sickness more likely.

Time traveling is messing with your computer's clock to advance the game faster - NOT recommended for VV2, since it makes it easy to wipe out your village and/or miss important things in the game.