The level of detail you provide in a publication date in your Works Cited list depends on the type of source and the information available. Generally, follow the lead of the source—if it gives the full date, give the full date; if it gives just the year, so should you.
Books usually list the year, whereas web pages tend to give a full date. For journal articles, give the year, month and year, or season and year, depending on what information is available. Check our citation examples if you’re unsure about a particular source type.