Wikipedia:Avoid contemporary sources

Contemporary sources, or real-time sources, include all sources about an event that are produced as new information comes out. They most commonly take the form of news reports, and they are contrasted with retrospective sources, which analyze an event from a historical perspective. Contemporary sources are rarely ideal, and they should be avoided when possible.

Contemporary sources and real-time coverage of an event provide the facts of an event, but they do not place it in context or determine its broader significance. News coverage and other contemporary sources are often routine, and even exceptional coverage doesn't necessarily indicate that the event should be mentioned in an article. An event that seems significant at the time can end up being insignificant in the overall scope of the article. Since it is difficult to measure significance and due weight using contemporary sources, using them to write content causes editors to make their own conclusions about significance and give the content disproportionate weight.

Instead, articles should use retrospective sources that were written later, such as books about the subject, journal articles that analyze it, or even newspaper articles that provide a long-form retrospective analysis of the subject. Tertiary sources such as encyclopedias are also useful for determining how much weight to give individual events as part of a broader article. Real-time sources about an event are primary sources for the event itself. They can be primary sources or secondary sources for people and places mentioned in the source, depending on how the source is used. Use of primary sources should follow the Wikipedia guideline on using primary sources.

The key is not to wait a certain number of months or years, but to compare contemporary and retrospective sources. Contemporary sources can still be written well after an event initially began or took place. If a crime is committed, real-time sources about the trial are still contemporary, even if the trial goes on for years. Likewise, if a disaster occurs, sources about the resulting investigation are still real-time sources because they entail publication of new information as it develops.

Biographies
When writing a biographical article, it is easy to collect several contemporary sources about the person and construct a timeline. This is a problem for two reasons. First, these sources may cover trivial things that aren't significant to the person's overall life. An entertainment article might mention that an actor attended the premiere of their movie, but that's not going to be relevant to their biography. Second, the sample of contemporary sources may not be proportional to what should be covered. An editor might happen upon three articles about a minor controversy involving the actor and two articles about their body of work, even if they're much more well known for their work.

Both of these problems are solved by using retrospective sources that cover the events and put them in context with each other. A full length book about a person will cover things that remained relevant and instruct on how much weight each aspect should have. Retrospective articles about specific events in a person's life indicate significance as well, and suggest they're still relevant to the person's biography later on. For lesser known people, use of contemporary sources is often inevitable. For well known people, retrospective biographical sources are most likely available and should be used. This is especially important for biographies of living persons, where the utmost care must be taken to keep them balanced.

Stand alone event articles
It is difficult to determine whether an event should have its own article while the details are still unfolding. At this point, contemporary real-time coverage is the only type of source available. In general, avoid creating articles about individual events until everything about the event has been resolved and retrospective sources begin covering it.

It may be reasonable to create an article for an event before retrospective coverage exists if the event has immediate societal effects on a national or international scale. This might include declarations of war, the sudden killings of thousands of people, the assassinations of world leaders, etc. Use common sense to determine whether an event has major self-evident ramifications. In situations where it's unclear, consider adding the information to the article of the person/place affected by the event with the option to split it into a full article after retrospective sources are made available.

Exceptions
There are two instances in which the use of contemporary sources may be good practice:
 * Basic facts: Real-time coverage of a subject is still valuable for basic, foundational facts. For a biography, it can be used to source things like birth and death dates, relatives, occupation, etc. For a building, it can be used to source the location, the date of construction or demolition, the architectural design, etc. Even then, these sources can be swapped out for higher quality retrospective sources if it is not a burden to do so.
 * Recent developments: When news is first broken about an event or a new development, there will be no retrospective sources about it. In this case, real-time contemporary coverage should be used to keep an article up to date. Use this cautiously, as it is still subject to the considerations listed above. If time passes and no later sources cover the event in retrospect, it should be removed from the article.