If you look inside the book in question, usually on the back of the title page (the page that says the title of the book and the author a couple of pages in) there will be a page that has all the information about the book. The copyright information can be found here. There will usually be a few copyright dates, depending on the age of the book. For example, the first ever copy of the book may have been published in the 1500's, but the edition you have is a revised version that was published in 2002. Also, if the book was originally written in a different language, there might be two different dates for that, too- one for when the book was published in its original language, and one for when the book was published in the language you're reading it in now.
For example: Inkheart, by Cornelia Funke, Translated from German by Anthea Bell
Published in Germany as Tintenherz by Cecile Dressler Verlag, Hamburg, 2003
Original text copyright © 2003 by Dressler Verlag
English translation © 2003 by The Chicken House
First published in the United Kingdom in 2003 by The Chicken House, 2 Palmer Street, Frome, Somerset, BA11 1DS.
I'm not sure the specific date but it was published sometime in 2005.
It is the date an article was published. It usually appears at the top or bottom of the article.
publication date or release date
If an article doesn't have an author listed, you can use the name of the organization or website where the article is published in place of the author. For articles without a published date, use "n.d." (no date) in your citation to indicate that the date is not available.
It was published on 17th December 1843
The U.S. Constitution was published for the first time on this date.
It was published in 2003
1234
November 2006.
1990
The "World Book Millennium 2000" was published in 1999 as part of the preparation for the year 2000. It aimed to provide information and insights into the new millennium and its significance.
If the website does not post it, then look for any copyright date and use the latest (newest) date. For example, if the copyright says, 'website.com - Copyright 2002-2007', then the published date of the website is 2007.