Trying to determine publication year, month, date

Using the API, I am to read the publication date (among other things.) But the publication date often only holds the year, and I also want the date and month (the month at a minimum). What is the right way to do this? Recent entries seem to have a “created” date close to the published date. However, this is not true for older entries. In particular, the earliest created date seems to be sometime in 2002.

Hello, and thanks for your question.

Our metadata schema has relatively few elements that are strictly required and many more that are optional (but encouraged, if available).

Only the publication year is required. Month and day are optional. So, if you’re not seeing the month and day in the metadata records from the API, that’s because they don’t exist. Either the publishers haven’t opted to supply them, or they’re just not tracked or stored by the publishers themselves.

A clearer example might be something like page numbers. We can’t require page numbers in the metadata, because many online-only publications don’t use them. But, when they do exist, they’re important for citation and discovery, because they’re one of the key ways to differentiate articles from the same volume and issue. So, we would encourage publishers to supply page numbers if they have them, but there’s no way to apply a strict requirement for them. And, indeed, you’ll find articles that do use pagination lacking page numbers in the metadata, just due to different (and not always ideal) metadata submission practices.

The created date indicates when the DOI was first registered. That’s why the oldest ones you’ll see are from 2002, when Crossref first started. For content published well before 2002, you’ll definitely find a big gap between the created date and the published date. But, that may also be true for more recent content.

For example, if a publisher just got around to joining Crossref this year and they start registering their current published content, the 2024 publications will have created dates and published dates that are quite similar. But, if that same publisher then decided (as we hope they do) to register their entire backfile, those items may have been published at any point in the past, including the more recent past. So, even though the created date will be from 2024, the publication date could be anything prior.

That’s all to say, there is no particular relationship between created dates and published dates.

Let us know if you have any other questions.