For the past six years, Apple has unveiled its new iPhones during the first week or two of September, either on a Tuesday or Wednesday. This means that possible 2018 dates are: September 4, 5, 11, and 12. Previously, if Labor Day fell on the 5th or later, Apple announced the iPhone the following Wednesday.
For 2018, Labor Day falls on Monday, September 3. So, if Apple follows its recent pattern, the company would announce its new iPhones the following Tuesday or Wednesday: Sept. 11 and Sept. 12. These dates fit well with the expected iPhone in-store release dates too, which are usually a week-and-a-half after Apple makes its announcements (save for specialty iPhones like the iPhone X and iPhone SE).
Since Tuesday is September 11th, it's likely that Apple will choose Wednesday, September 12th for its iPhone event. The company is expected to unveil three new iPhones including a new 5.8-inch OLED iPhone, a 6.1-inch LCD iPhone, and a 6.5-inch OLED iPhone.
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