Depends what clothes I’m wearing when it happens.

If I’m wearing anything that could remotely be seen as fancy back then (which I mean a lot of modern clothes could pass off as), since I’m near the ocean, I’d immediately run into the water not seeing anyone, and then pretend I’m a royal foreigner who ended up shipwrecked. Since I usually wear a watch, have a tungsten (Wolfram) crystal wedding band as well, that would help me in passing off as royalty as well. This is assuming the people helping me aren’t brigands. There’s things we do and know of that we take for granted that could be used to pass off as someone upper class too, like reading.

Then next steps would be to get to an aristocrats home, and eventually I’d imagine somewhere where I could work with scholars so they can teach me the language and we can work on translation so we can understand each other. Would have to be extremely careful of smallpox during all this of course.

Once we could, that’s when I’d finally whip out my phone to trusted scholars and pull up my survival books, books on plumbing, etc specifically, and to explain that this is a special metal and glass book that can hold many books that’s common in the land I’m from, and that I can teach them how to build them. But that we’d need to build plumbing because I’d like a shower by then.

I’m on the Gregorian calendar, 650 years ago is the year 1375. I’m in North Carolina, so if I were to snap back in time at my present location I would be a blue eyed white guy in pre-contact North America. And while I think I’m an above average candidate for the Connecticut Yankee in King Arthur’s Court scenario I’m not realistically able to start “from scratch.” I’d probably make it the summer on forage and my own body fat. I don’t picture encountering the natives going particularly well, for me or them. I’m not sick and I’m vaccinated against a lot of shit but watch I’ll give them 6 centuries worth of influenza updates.

I don’t think it would help that much being plunked down in 14th century England; we’re talking Geoffrey Chaucer’s lifetime here, to them I’d sound insane. Modern English is a few hundred years off. If they didn’t trepan me to let the demons out of my skull and I didn’t die of smallpox, I’d try to invent the electric motor 500 years early and be burned for heresy or some shit.

Wash my hands

I’d die pretty quickly.

There’s a former nunnery down the road. I suppose I’d try to join. Or maybe find a farmer who’s looking for someone to look after his kids because his third wife died in childbirth.

I would fall from a very high place

Many years ago when I thought about this, I realised I wouldn’t be able to put much of my modern knowledge and skills to use. I decided I’d learn to make basic matches by distilling urine into phosphate, which wasn’t invented until the 19th century, but I’ve forgotten the process. Collect lots of urine and boil it? Also, if you make white phosphate it can cause horrific toothache and they have to remove your jaw… So, I’m hoping another commentor will suggest a safer skill I can brush up to be ready for travel.

As an Australian I would struggle significantly unless you were to also transport me geographically.

650 years ago this place was a sea. So I’d end up having to swim at least a couple of kilometers. Considering the current sea temperatures, I’d probably die of hypothermia before I could reach the shore.

I’d make some fucking soap.

612 years in the past
In Brazil. So almost a century before the first europeans landed here. I’m assuming I just plop exactly in my relative earth-location, but in the distant past. (… It would be really funny if this was overly literal, because I’m currently in the 12th floor, so I’d thanos snap into the past and immediately fall to my death)

Well

As a person from modern times – From AFTER the Americas came into contact with Europe, if I went near a person here in the Land of Palms (that’s what the natives called Brazil!) from those times we’d both get horribly infected and die a lot due to how antibodies work. Viruses did a lot of the legwork in genociding the natives. Euros would deliberately do things to infect natives so they’d die of illness.

The place I currently live in is slowly turning into a desert, but was a deep jungle back then (… It was still a deep jungle in the 1910s tbqh).

… I think I’d just die? Become food for a jaguar or eat a poisonous fungus or sth.

Would love to indulge in the fantasy of giving the Guarani people guns and a warning to shoot white people on sight just to see how history would change, but that ain’t happening.

Edit: I’m taking the middle road here and assuming something around year 1250 or so, not 1100 or 1400 as confusingly set in OP.

Okay, so unlike most other scenarios, I think I would be fine for a while at least. The peoples living where I live would have made and kept more or less regular contact with the sons of bitches from the south that would later crusade us (or I think maybe one of the crusades is presently ongoing at the time…) so while I would both introduce and be hit with diseases or more likely strains of familiar ones new to my body/their bodies, I think it wouldn’t be as destructive as entirely separated landmasses like America vs Europe.

So if I survive the shock my body gets hit with, and I don’t kill everyone around me, I think I would be fairly well received. As far as I’ve read, the languages and dialects were different than after the formalization of the written form, and at this time these lands were just starting to get forced under Swedish rule, so with my basic understanding of Swedish and of course my native language, I think I would be able to communicate well enough to not get instantly killed as a demon or something.

I think my best bet would be to introduce myself as some sort of demi-god, a bastard son of the god of forests and the hunt probably, which would hopefully explain my alien attire and materials used to make them. And the alien accent/dialect of both the local language or Swedish, depending on where I’d land. If the first contact I make aren’t local but crusaders, I suppose I’d have to try and push myself as a wandering preacher of Christ or something. I’d have to hope they’d speak Swedish, since I do not know German well enough to form two words together, and they’d likely be the next likely encounters. Novgorodians I think were fine with the Swedish language in general, so if our current knowledge of history was off enough that I’d meet them here, I’d still be fine. No idea what I’d pretend to be to them though. My limited knowledge of history doesn’t help there. But as far as I understand, they were sort of a melting pot of close-by cultures, and not so focused on these lands at this time, they’d just take me for a local hermit and let me run off clumsily.

If I was able to survive the first encounters and get myself to a village or a hillfort, I’d try and establish myself as a wise one, helping with calculations and engineering and whatnot to the best of my capabilities, which I would think honestly should far exceed those of the locals at the time. So maybe I’d get by just for being useful and knowledgeable.

But I don’t think I’d live a long life. These were a turbulent and violent time and one village elder or the other, fancying themself a king or whatever, would just send assassins to off me for being an asset for the local leader where I’d end up in.

Even if I’d travel to avoid this problem, it probably wouldn’t take until my old ages to have someone or something off me just by happenstance. And I wouldn’t want to live a hermit in a time where internet or computers aren’t a thing. I think the only way to cope would be to focus on a family, try and bring up children and have that fulfill my life as best it can, as long as it can.

Honestly, I consider myself lucky in this scenario. We still have our language alive and in use, the same the locals would speak at that time. This together with the general superstitious nature of the local tribes — which the crusades and Christianity, with overt blood and sadistic violence, would (thankfully later, I hope for my sake here, at least according to our current knowledge) succeed in some amount to water down and turn them to its specific flavor of lame ass superstition — would make it probably at least somewhat likely I wouldn’t be killed on sight or something to that effect.

Assuming I’m snapped back to the same part of the earth, climate-wise that’s ideal in the US PNW coming out of spring. Plenty of berries and food to forage, and I’ll probably impress the natives with my watch and well made clothes. I can probably get the native tribes to metals, and gain acceptance with my magic hand tool that will briefly shine light at night for a few weeks. I don’t know offhand where copper would be, but I know gold is in the streams, and I know how to placer mine, so I can get some electricity going with that and magnetized rocks from lava flows.

I think first contact would be the key.

Wait 612 years and buy Microsoft.