When you are able to ask questions of the masked guy after your 2nd excursion in the past he mentions that is the only working time machine and it works on 20-year skips.Unless I've missed something...you/we know this....because?
Again, unless I missed it (and I've not played the update yet), no one has told us there is only one...no one has said it only works in 20 year increments. If that is niot explicitly stated, then it isn't a fact. If that is explicitly stated in the new update, then ignore my post.