Works published before which year are internationally in public domain?
<p>Figuring out whether a work is in public domain can be quite complex as different countries have different rules and there are often a lot of (relatively) complex exceptions. There must however be a cut off point before which you can be sure beyond any reasonably doubt that the work is in public domain. Which year would this be? Or put differently: What is the oldest work which is not yet in the public domain?</p>

<p>And just for the record, I am aware that this might be a bit of a complex question, but it seems to be quite a reasonable question, especially if you would wish to use the work for some product that you wish to distribute internationally (e.g. <a href="https://gamedev.stackexchange.com/questions/105240/can-i-include-a-public-domain-book-in-my-game">this question made me think of it</a>). Now, I do realize that other issues can come up (trademarks, later editions and moral rights for example), but to keep the question reasonable just ignore those (though as an aside they are fine).</p>

<p>See <a href="https://commons.m.wikimedia.org/wiki/Commons:Copyright_rules_by_territory" rel="nofollow">World Copyright Terms</a>.</p>

<p><em>If</em> this is an accurate reflection of current laws and <em>if</em> those laws have not changed, then the country with the longest terms is Mexico at Life + 100 years; it's a reasonable assumption that most authors don't live more than 80 years after first publication so anything before 1835 is probably fine.</p>

<p><em>But</em>, the laws in Mexico <em>have</em> changed and works whose authors died in or before 1952 are in the public domain.</p>

<p>This demonstrates why it is impossible to give a general answer applicable to all works. A definitive answer can only be determined by:</p>

<ol>
<li>Identifying the work</li>
<li>Determining the originating country or countries; online publication in particular will create more than one.</li>
<li>For each of those, determine the law in force at the time of publication and the copyright duration that results</li>
<li>For each of those, determine if changes to the law have affected the copyright duration</li>
<li>Find out when the author died</li>
<li>Determine copyright status</li>
</ol>

<p>This is a non-trivial endeavour.</p>

copyright international