I do understand that citations should be as precise as possible (including e.g. edition of a book or a page number), so that ideally, the reader can find the information exactly as I found it when writing.

I also understand that the problem with citing webpages is that they can change. But how does including the date when I accessed the page help anything? The reader still won't be able to read the same version I did (unless the page includes history, which is very rare). And comparing the accessed date with the current date isn't very helpful either: some webpages change multiple times per day, some aren't modified for years.

Or is the accessed date useful for some other purpose?

  • 6
    The reader still won't be able to read the same version I didarchive.org/web/web.php
    – JeffE
    Jan 4 '13 at 17:41
  • 3
    @JeffE That works only on old pages (several months old). And not all pages are archived there.
    – svick
    Jan 4 '13 at 18:04
  • webcitation.org/archive.php
    – Orion
    Dec 4 '14 at 21:36
  • 2
    For Wikipedia, if you know the date, you can find the exact version. If you don't, then who knows what changes will have taken place since you cited it. Dec 5 '14 at 0:53

I am not aware of any published accounts of how style rules are developed. If you really want to know why a particular rule was developed, you need to asked them directly. That said, there are a number of different styles for dealing with electronic materials and these styles are changing:

  • MLA: You always need the date of access for electronic resources.
  • APA: You rarely use the date of retrieval, although in previous versions (APA 5) you always did
  • CMS: You never need the date of access/retrieval. I am not sure if you ever did in earlier versions.
  • 1
    This answer really doesn't address the OP's underlying question. It essentially says: "i don't know, ask someone else..."
    – Paul
    Dec 5 '14 at 4:04
  • 2
    @Paul my point was 3 of the big players in terms of style guides recommend different things and at least one of them recently change its view. To me this means there is no definitive answer.
    – StrongBad
    Dec 5 '14 at 8:39

A URL does not refer to content, it is only an address. Since you are making a claim about what was written at that address, you must associate a date with it, or it is meaningless.

If you do such a thing, you should also save the content, in case it is not recoverable and you want to refer to it again or support it further.

  • So you're saying it's important to uniquely identify what I was reading and it doesn't matter whether anyone else will be able to read it too?
    – svick
    Jan 4 '13 at 18:35
  • 5
    Not that access doesn't matter, just that uniqueness does. Jan 4 '13 at 18:39
  • 1
    +1 It is really about identification. So sure, there are cases when the date is not necessary, DOI is one such for example (it's moreorless just a web address, but its contents should be stable in time).
    – yo'
    Dec 4 '14 at 22:20
  • The content you get can depend on other factors than just the date. URLs often produce different content depending on your IP address, your user-agent, and cookies. It is even possible for a page to be written in different languages and automatically have it delivered in the language, which the user chose in their browser.
    – kasperd
    Dec 6 '14 at 22:41

If you know the URL and date, you may be able to use The Internet Archives (a.k.a. the Wayback Machine) to see the page, if it didn't change too frequently.

  • 1
    This is not the reason why you include them, it's just an added bonus. The reason really is identification.
    – yo'
    Dec 4 '14 at 22:18

Most URL cited are institutional sources, the kind of guys that can provide reliable information*. If a reader finds that your claim does not coincide with the information they can find at the moment, they can contact the administrators of the page and ask. Certainly, it is easier to get the correct copy if you have an specific date.

In Bioinformatics it is common to use web servers to run some programs (example). In this cases, the dates are important for replicability, even when citing the program version, because the specific software versions it depends on may not be public (say, before March 15th, AwesomePredictor.com had installed BLAST+ 2.1, and after then they installed v2.2).

  • One could cite less formal sites to support side points like "this and that have been in the focus of popular culture", but these are ephemeral by nature.

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