If I order virtually anything else online, it comes in a week or so, including shipping time. Yet when I sign up for a magazine online, directly from the publisher even, it will usually say "Please allow for 6 to 8 weeks for your first issue to arrive. " And it’s not just a cover-your-ass kind of thing, it often does take that long.
So what’s the deal? Why can’t the magazine publishers get their act together?
Because of the pipeline. They put your name into the database, but labels for the next issue are probably already printed up. If it’s a monthly, you have to wait an issue. If the latest issue has just been mailed, you may have to wait two issues.
Here’s a helpful hint:
One of the first pages of the magazine will have a block with the names of the publisher, editors and such. There is a phone number in this block. Call that number if you have a change of address or want a new subscription. You will be entered in the data base instantly and will most likely receive the next issue where you want it.
Haj
For future reference, the block of names, positions, addresses, etc is called the masthead. 
I have two possible explanations for such long delays and it’s not the database, that’s a couple of computer clicks.
Many magazines print up thousands of copies of a particular issue that are leftover, which rather easily be used to fulfill brand new orders.
But in order to get a discounted postage rate, there must be certain numbers as to zip code and new daily or weekly subcription numbers may be insufficient to quality.
Second, the ad rates are probably negotiated well in advance based upon distribution and in some cases they can’t be quickly changed or the advertisers require proof of mailing numbers–it’s impractical to keep updating those numbers.