1795

While trying to work out how a forest had grown on Earth overnight, the Twelfth Doctor compared a tree to a time machine, and determined that this had to have happened due to messing with the fabric of time, as "you [couldn't] create a whole overnight forest with extra special fertiliser". He said that "[y]ou plant[ed] a little acorn in 1795, and in the year 2016, there [was] an oak tree, there in the same spot, with a tiny, little bit of 1795 still alive inside of it." (TV: In the Forest of the Night)