Would you bother preparing something to help prove your reincarnation, or would you simply take advantage of whatever you retained (and prepared for yourself) from your past life?
How might you use this ability to help yourself and others?
Edit:
To clarify, suppose you have some vague memory of your past life in your reincarnated self that helps you along and allows you to take advantage of whatever your past self prepared for you.
because we know what happened in the 1500s - with a little bit of foreknowledge about when comets and whatnot are going to occur with some basic modern chemistry or engineering know how, you could easily set yourself up as a prophet/philosopher-king. seriously, easy-mode reincarnation.
picking a future year just increases the likelihood of being an Elysium style factory slave. pass
You mean until the church deems you a heretic and kills you right? It won't matter that you got predictions correct. Hell, that will only give them even more of a reason to deem you of the devil because only God has the power to see the future! To the pits with you child of Lucifer! Don't forget you are talking about people who went to wars because some people didn't believe in their sky daddy and only their sky daddy is the right one.
They want to go back to the dark ages with a load of potions and prophecies.
Someone's speed running being burned as a witch…
it's easy enough to lie your way out of persecution - church officials do it all the time (it's dogma).
It is today, back in the 1500s when the church was the law and government and could do whatever they wanted with basically no repercussions, not so much.