Update: iPhone will be released on June 29

UPDATE on 6/4: Some weeks after this item was posted, Apple revealed its release date for the iPhone: On the first Sunday in June, the company said the iPhone would be available June 29 and began running a series of ads featuring the device.

ORIGINAL POST STARTS HERE: Ever since Steve Jobs' keynote at the Macworld Expo in January, we've known that the iPhone is being released sometime in June. But we haven't known exactly when.

Now Cingular is confirming that the release date will be June 11. A customer service manager at Cingular (we called 800-947-5096 and were transferred to sales) gave us that date late Thursday, but, alas, said he didn't have any additional information beyond that.

That date is no coincidence. It's the first day of Apple's Worldwide Developers Conference, scheduled to be held in San Francisco from June 11 through June 15. (Incidentally, the agenda includes a focus on Leopard, the next generation of OS X that's supposed to be released sometime in the second quarter of 2007.)

Rumors have been swirling about the iPhone release date. One blog pointed to a release date of June 15 based on alleged documents filed with the Federal Communications Commission, but those have been shown to be a hoax.

Here's some information from our sister site, CNET.com, about the iPhone.