The iPhone 5S and iPhone 5C will reportedly go on sale on Sept. 20, four days after iOS 7 makes its debut on Sept. 16.

After numerous rumors and speculations regarding Apple's iPhone launch plans, it looks like Sept. 20 is the big day when the next-generation Apple smartphones will go on sale.

Apple is expected to hold a press event in the U.S. on Sept. 10, where it will likely announce its new iPhone 5S, as well as the much-rumored budget iPhone 5C. Both smartphones are rumored to become available for purchase starting Sept. 20 and Apple will reportedly release its latest iOS 7 on Sept. 16, according to TechManiacs (translated).

While these rumored dates are not confirmed, they do make sense from a historical point of view. For the past six years, Apple has launched its new iPhone more than a week and less than two weeks after officially unveiling the device. The company also tends to launch the device on a Friday, giving users a full weekend to learn the ins and outs of the new iPhone. With these hints in mind, the most likely launch date seems to be Friday, Sept. 20.

The iPhone 5C is expected to launch as a lower-cost iPhone with similar specs to the current iPhone 5. To keep the costs down, however, this model will reportedly come with a plastic casing, which will be available in various colors.

The new iPhone 5S, meanwhile, is rumored to boast a number of hardware upgrades over the current iPhone 5, including bumps in the processor, graphics and RAM departments. The smartphone is also expected to pack a built-in fingerprint sensor, likely located on the Home button.

Apple has not yet announced nor confirmed these two handsets, which means that for now both the iPhone 5S and the budget iPhone 5C are still in the rumor state. Judging by reports and Apple's previous launch schedules, however, it seems increasingly more likely that new iPhones will make their debut as soon as next month. If rumors prove to be correct, Apple will make an official announcement on Sept. 10.