Okay, so if I was to time travel a few hours back, get the turnips, then fast forward to current time, will the turnips rot? What if I did it tomorrow? Say if I went a day in the past and bought the turnips then fast forwarded one day later to current time. Would they be rotten?

I just went back in time and then traveled forward 5 hours and my turnips are fine. My friend said once you buy turnips, don't time travel backwards, and don't time travel forwards past a week.

Turnips will spoil only after you buy them if you time travel backwards in time or to the next Sunday onwards