We might just found our first reliable iPhone 5 release date rumor, and October 21 is looking like the magic day to mark on your calendars. The Verge has received a tip from a Best Buy employee that suggests the retailer is set for an ‘Apple fixture’ installation on the 21st.

What makes this seem so plausible is the continued rumor that October is indeed the timeframe in which we should expect an iPhone 5 to go on sale, with an announcement coming some time in the next few weeks. Does Best Buy know something we dont? It’s entirely possible…

The tipster says that while the instructions from Best Buy are intentionally vague, such occurrences don’t happen often, and a similar request for a member of the management team to be on hand was also part of the iPhone 4 launch documentation.

It’s clear that Best Buy is expecting something from Apple on that date, and it has to be something that both parties deem worthy of a new point-of-sale.

The date also falls nicely around a planned meeting of managers of Best Buy’s mobile devision, according to the source, suggesting plans may be afoot.

“On a related note, our tipster tells us that Best Buy Mobile managers have a meeting scheduled for October 10th to “discuss upcoming BIG release dates” (emphasis his). Assuming we get an Apple press event for the new iPhone a few weeks in advance, the managers would be well aware of the release date in time to discuss it at that meeting, so that’d support a release on or around the 21st, too.”

We’ve been more than a little skeptical about such rumors, and possible release dates are always tricky to pin down, but this does have a good feel to it. Did we just find out when Apple will bring its next iPhone to market?

We’ll let you know when we find out more!