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I start every .java file in my project with a license (BSD, in my case). And its first line says:

/**
 * Copyright (c) 2011-2014, Firstname Lastname
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 etc.

The question is, why do I need to show years there? I see many other projects are doing the same. What will I lose by just saying Copyright (c) Firstname Lastname, without that time interval.

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marked as duplicate by gnat, MichaelT, Kilian Foth, GlenH7, Dan Pichelman Feb 6 at 17:09

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Closely related: programmers.stackexchange.com/questions/210472/… –  apsillers Feb 5 at 15:52
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1 Answer

Dates aren't so much a licensing thing as a copyright thing.

Although the particulars vary from jurisdiction to jurisdiction, copyrights generally apply for a finite amount of time. By including a date range, you can state unambiguously when the term of your copyright started, and thus remove the question of whether or not that copyright is still in force. Computing is a young enough field that this is not presently very much of a concern: most of the code that has ever been copyrighted still hasn't been around long enough for the copyright to expire. But as the years go by, it will eventually start to be an issue.

In some jurisdictions, you can release the copyright on your code by dedicating it to the public domain. However, even in these cases, the date stamp remains important. Stamping public-domain code shows unambiguously when it was released.

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Copyright (c) 2014-2999 ... –  Michael Feb 5 at 16:45
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The start date is the important part, really. The end date doesn't matter as much, since it's recognized that sometimes things go for more than a year without being updated. Even if your datestamp goes beyond what the law would specify is the term of your copyright, the law wins. –  The Spooniest Feb 5 at 19:54
    
So, why do so many people and corporations bother themselves updating the end date in a lot of files? –  brandizzi Feb 5 at 20:31
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Historically, for a work to claim copyright protection, it needed to have a notice which indicated when it was published. Copyright protection would expire 28 years after January 1 of the specified year unless renewed. If parts of a work were published in any form in 1919 and other parts were first published in 1920, claiming a 1919 date for the latter parts would cause their copyright to expire a year earlier than it otherwise would; claiming a 1920 date for the former would void their copyright entirely. –  supercat Feb 5 at 20:37
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In an over-reaction to the fact that some people's works were forfeited to the public domain because of accidental failures to include copyright notice, the 1976 copyright rules basically threw out copyright notice requirements. Still, despite the fact that for many works the date given in the notice is unlikely to affect when, if ever, they enter the public domain, the inclusion of copyright notices is still common practice. –  supercat Feb 5 at 20:41
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