Conspiracy theories are an unfortunate, paranoid and counterfactual outgrowth of any national tragedy. But in the aftermath of the mass shooting at Navy Yard, so-called “truthers” found some hard proof that something was off: The attack happened on Sept. 16, but both and British Columbia's Kelowna Daily Courier published stories dated the day before.

Thousands of people, including some of the Internet’s most popular conspiracy theorists, seized on the time stamps as evidence of a vast government conspiracy to orchestrate tragedies and clamp down on gun rights in the aftermath. They have other “proof” too, of course -- conjecture about “crisis actors” and John Wilkes Booth and the two rumored shooters who didn’t end up being part of Aaron Alexis’s plot. But the time stamp issue is the foundation of many of the more popular videos circulating on YouTube, Facebook and that seedy corner of the Internet where people debate the Illuminati and UFOs.

“Now we have what might be the best smoking gun evidence yet, and it is time-stamped from September 15,” rails the popular conspiracy vlogger Dahboo77 in a YouTube video that has been viewed more than 90,000 times. “These guys must have put this into the system right before midnight, right before they left the office, on the 15th. And they knew it” -- “it” being the Navy Yard rampage, hours before it happened.

The reality is, of course, a little more mundane: Both sites incorrectly ingested a feed from the Associated Press, which caused their AP stories to display the wrong time stamps.

A little background in wire services is helpful here. The AP is such a service, which means it centrally produces and distributes news stories to thousands of media outlets around the world. These outlets get a “feed” of all the AP’s stories, which they pull into their computer systems and, in some cases, publish automatically online.

AP’s first wire on the Navy Yard shooting went out at 8:43 a.m., minutes after police began receiving calls. (AP spokesman Paul Colford confirmed there was no error on its end.) But two Web sites, of all those thousands, carried the wrong date. Why?

Jon Manchester, the managing editor of British Columbia’s Kelowna Daily Courier, attributes the mistake to a long-standing error in the site’s time zone offsets. When the Daily Courier publishes a wire story from the AP, it automatically changes the story’s time stamp from Atlantic to Pacific time. But because the wrong time zone offset had been selected in the Daily Courier’s system, the times were wildly miscalculated -- not only on the Navy Yard story, one blogger observed, but on everything the site published from the AP. The Daily Courier fixed the time zone offset Tuesday afternoon.

“It was done just to set it right, as it had been off for some time,” Manchester wrote in an e-mail. “I suppose the conspiracy theorists hounding me yesterday with phone calls prompted it.”

ABC suffered a similar problem: While the network received the AP feed Monday morning, a technical error caused the story’s time stamp to read Sunday night. ABC declined to discuss the details of the error with The Post, and it’s unclear whether the mistake originated on AP or ABC’s end. But there’s no doubt that the story did, in fact, publish online Monday morning -- it didn’t appear in Google News before then, and Google crawls media sites for new stories several times an hour.

Unfortunately none of this is likely to impress Dahboo77, whose shtick derives from willfully ignoring facts.