Those two locations are Japan and Greece, and both markets are typically first-tier for Apple releases. The September 20th date is just ten days after the rumored keynote, which would make sense: it would allow time for Apple to seed a finalized version of iOS 7 to developers for testing, and allow shipments to be sent to retailers and carriers across the world.
Apple typically rolls out their devices by phases: countries like the US, UK, Australia, New Zealand, Japan, and others usually receive the new hardware first. Subsequent rollouts follow. This is partially required due to supply constraints, but it also has to do with legal ramifications. For instance, the Chinese carriers and government have multiple hoops that companies have to jump through to have their device sold in the country. Apple has been one of the best smartphone makers in terms of device rollouts, and it seems like that trend is set to continue.