If they sing “popular” songs that you’ve never heard, and if you question them about it they say, “Oh, it’s popular where I come from. It must be a regional hit.”
You could check what kind of underwear they have on.
No seriously anyone could put on a period costume and pass as say a 1870’s cowboy but they could easily miss the correct underwear part. Underwear is not covered well in history books and I doubt a time traveler would get it right.
That was part of the joke in BTTF where Marty was wearing Calvin Klein underwear.
Well, a visitor from 2067 or later would be unable to supress their exaggerated, alarmed response when anyone around them sneezes.
Or possibly an excessive and encyclopedic knowledge of current pop culture would be the obvious markings of a time traveler because they have thoroughly studied the period rather than experienced it. I have always been told that immigration officials investigating marriage fraud are more suspicious of couples that seem to know every little detail about each other (because they have memorized a huge number of facts) than the couple that have natural gaps in their knowledge (i.e., the husband that has no idea what his wife’s face cream is because he doesn’t buy or use that stuff, etc.).
Assuming for the sake of argument that you’re right and a time traveller may arrive wearing the wrong underwear, wouldn’t said time traveller buy stuff upon arrival?
I don’t think radiocarbon dating would work. Radiocarbon dating measures how long the organic material has been dead for. Carbon 14 is continuously generated (replenished) by cosmic rays, so there is a fairly constant amount of it in the earth’s atmosphere. After an organism dies and stops incorporating fresh carbon from the environment, the C14 will decay and not get replenished.
By the way, I too am trying to think of the short story JacobSwan mentioned and am drawing a blank. Bradbury? Orson Scott Card?
If you read the linked paper — C-14 levels spiked when we started atmospheric testing of nuclear weapons, and have been steadily declining since. The spike and the gradient of decline is how we can get 1-year resolution for the last few decades. Assuming that we don’t start nuclear testing again, somebody born in the future will have less C-14 in their living tissue than somebody alive today.
I was wondering if they pretended to be an orphan, or came from a destroyed community. Creating fake orphanage records would be possible, although orphanages are very rare these days. You’re right that this would narrow the suspect pool.
Another good idea is to be a foreigner. This explains the accent and lack of familiarity with the language and idioms, lack of knowledge of current events and popular culture… and makes it a bit harder to track their background. They had better pick a country that hardly anyone knows anything about and be able to “pass” as one physically.
If their technology is more advanced than ours, I figure they’d get vaccinations, much like someone traveling to an exotic country today would have.
I suspect that a time traveler would have to deal with “time traveler syndrome” when they first travel, and it could take months to get over.
I read that story too, but darn it, I can’t remember the title or who wrote it.
Perhaps the time traveler originated in 2016, because I’ve never heard of the notion of pulling up your trouser legs to avoid wrinkles.
I’m pretty sure it’s in a collection of short stories that I currently can’t find. Either a time traveller has removed it from the timeline, or one of my sons has borrowed it. I’ll check their bookshelves later.
It’s a damn shame that the answer isn’t A Wrinkle In Time.
Sorta thing Ward Cleaver would do before sitting down in the living room to read his Sunday paper, having previously loosened (slightly) his tie.
Ray Bradbury, and I forget the story, but remember that detail oh so vividly:)
Also, you’re not pulling up the legs to avoid wrinkles, but to make it easier on the, on the, uh, um, boys.
Check their teeth. Tooth decay will be eradicated in the future.
No, it’s to relieve the stress on the fabric, and keep the knees from becoming baggy. When you bend a vertically arranged articulated process covered with clingy fabric, it tends to bulge out the material at the knee. Over time, this continuing stress stretches the fabric, so when the wearer stands up, he gives the appearance of someone wearing old poorly maintained clothing, which in an earlier era was not the badge of honor it is today…
seems straightforward.
if an individual is getting very sick from common diseases, he is a time traveler from the past.
if an individual is getting everyone around him sick, he is a time traveler from the future.
Or the other way around. I get confused on this issue… 
Look for people who don’t seem to age like Patrick Stewart.
A few people have mentioned language and I think that is correct. Anyone remember the 1800s idiom, “Wouldn’t know a “b” from a battleclave” (describing someone like a washerwoman who can’t read)? Or the 1600s idiom, “As queer as Dick’s hat” (a reference to Richard Cromwell’s early desire to crown himself King of England)? Both idioms have fallen out of fashion. If your suspect doesn’t recognise the meaning of “Brexit” or “GFC”, that might be an indicator.
There was a novel called “Millennium” in which a time traveller with an American accent did not recognise American coins and so just dumped a pile of them onto a counter like a foreigner. Another possible indicator.
Fashion might be another indicator. If someone youthful was to walk into my office in a thin red leather tie and a jacket with shoulder pads I would wonder what was going on. I wouldn’t have had the same reaction in 1985. Sloppy study of fashion by a time traveller might give him or her away.