What’s the point in dating magazines one month in advance?

The only print magazine I subscribe to anymore is Consumer Reports. Earlier this evening, I was thumbing through the October issue, which actually arrived in the mail over a week ago, when this question came to mind. Typically, just about every mainstream magazine is ready for sale a month in advance of the issue date on the cover. What’s the point in doing so? Surely, magazine publishers aren’t trying to fool me into thinking the contents are more timely or that they’ve somehow scooped everyone else by getting the news into print earlier. Why not just sell September’s issue in the month of September, instead of August?

Simple.
Keeps the magazine on the racks for an extra month.
You can buy September’s edition on August 1, but when someone picks up the copy on September 25th, they think it is still current.
Twice the time to sell copies = twice the income from news stand sales.

But when the October Issue comes out in September, do you have both issues on the stands for the month of September? Because I haven’t seen that (that I’m aware of).

This is a WAG, but I would guess that the practice originated back when distribution was based on a reliance on manual coordination of thousands of subscriptions and was heavily dependant on labor intensive practices.
For any issue of any large circulation magazine, they had to employ hundreds of clerks to sort through current subscriber lists to come up with the number of base copies to be printed, then add to that the number of newsstand copies that had to be projected. Following that, the magazines had to be printed, then mailing labels had to be pasted on and the magazines had to be sorted by postal district for delivery to the post office. They also had to factor in a buffer period to ensure that all the magazines were printed, labeled, sorted, and bundled for shipment in time to make it out the door with enough lead time for “timely” delivery.
Once that cycle was established, (some time in the early 20th century), the companies sort of locked into that cycle as the normal working month. As automation kept stripping days out of the need for the cycle, the magazines needed less lead time to get the magazines out the door, but since they already had their business cycle established, (and since any magazines that allowed their print cycle to slide back to keep the dates in line with actual delivery would have then faced having their competitors note that they were “late”), they simply left the cycle alone and allowed the dates to creep up into the prior month.

Even today there is an enormous amount of manual reconciliation between the printers and the circulation departments (often farmed out to third-party sub-contractors), that results in the typical “Allow six to eight weeks for delivery of your first issue” statement.

(And I am aware that weekly magazines do not suffer the same situation, exactly, but my guess, there, would be that the economy of scale for the (relatively) fewer weeklies allowed those companies to take advantage of automation sooner and to use automation to keep the dates aligned more closely.)

Comic books were advance-dated by three or four months for most of their publishing history. Publishers competed for limited rack space, kids wanted the newest and latest, and until about ten years ago, the cover dates were seriously out of whack with the actual publication date.

There is probably a factual answer to this one.

Moved from IMHO to GQ.

According to Cecil Adams the date displayed is the sell-by date, or the one by which the magazine ought to be removed from the newsstand.

Exactly. The date printed is the date on which the sellers should remove the magazine from the newsstands.

Just yesterday I picked up a copy of The Physics of Superheroes by James Kakalios, which includes a brief history of comic books in the introduction. Kakalios offers this explanation:

It’s for the convenience of the newstand owner. If a magazine comes out in September and has “September” as the date, the person selling it has no way of easily seeing if the magazine is monthly or quarterly: he’d have to open the magazine, look in the subscription information, and then try to remember it. If you have the “sell by” date, he can determine when to pull the magazine by just looking at the date.

Sometimes, they even acknowledge it. I subscribe to PC Gamer, and in one recent year, they had their list of “top ten scary games” for Halloween in their November issue.