Reality glitch

A reality glitch is an instance where commonly accepted continuity changes for one or more people. This can be something as trivial as someone's name being a letter off to driving a 5 hour drive in 30 minutes.

The cause of reality glitches isn't known to any degree of certainty, and from all that's known, they can happen at any given point in time to anyone with no clear trigger.

Types of Glitches
While there may be infinite number of possible types of glitches one can experience, there are a few that pop up frequently enough to merit classification.

Alternate Timelines
These are changes in the continuity of a historical timeline. This includes sequences of events (ordering them wrong, some event never happened, etc), the existence/status of people (such as celebrities being remembered dead but still alive), and the geological locations of countries (to name a few). This is perhaps the most common type of glitch, with a large number of people remembering, for instance, that Nelson Mandela died in prison or remembering New Zealand being in a completely different place than it is now.

Unfortunately, this type of glitch is particularly hard to prove, as it relies entirely on an individual's memories, and false memories form very easily. This is a less satisfactory answer for more extreme cases, such as remembering conversations about the death of a relative only to find that no such conversation had occured and the relative is not actually dead, though such stories still rely on the individual's trustworthiness.

Time Loops
A time loop can be considered something like an extreme déjà vu, where an individual literally sees the exact event twice in a row. Additionally, some may argue that a déjà vu is just a more minor reality glitch.

Impossible Routes
These are cases where one or more individuals are traveling to a distant destination, and find out later that either the route they took wasn't on the map, in the wrong direction, or took significantly less time than should even be possible. Unlike some other forms of glitches, these can be physically verified immediately afterwards (at least in the case of the amount of time taken vs the distance) as well as the potential for more than one witness, assuming yet another reality glitch doesn't happen such that only one individual involved remembers the incident afterwards (which is a fairly common occurrence in reality glitch stories). Unfortunately, due to the spontaneity of such events and the lack of understanding of the trigger, it's nearly impossible to take scientific measurements before it becomes mere hearsay.

Time Travel
There are some very rare stories of people experiencing a form of temporary time travel in which they meet their future selves or see the past/future and return soon afterwards.

Researching
Due to the nature of reality glitches (rare, spontaneous, based on an unknown trigger, and having a reliance on individual perception), it's difficult to impossible to directly record and research the phenomena. Until a reproducible trigger is found, they must necessarily be studied via the comparison of the thousands of stories available online. This poses problems such as difficulty of determining who's telling the truth, as well as the possibility of the very existence of such stories affecting them in some subtle subconscious way via cultural osmosis.