The passage of the Earth around the Sun. The birth of Jesus of Nazareth. The release of Apple's iPhone.
All events that mankind has set his calendar to - but a shift in Apple's annual iPhone habit might be about to change all that.
Since its launch in 2007, a new iPhone has been released every year. As of 2008, Apple has stuck to a cycle of adding incremental improvements every other 12 months: one year would get a 'major' upgrade, while the following would get a smaller 'S' upgrade. 3G was followed by the 3GS, followed by the 4, followed by the 4S - you get the idea.
According to Asian business publication Nikkei Asian Review, Apple could be in the midst of shifting from its two year cycle to a three year system.
2016 has already seen Apple break its own habits, releasing the 'affordable' SE back in March. The evidence is mounting that the iPhone 7, expected to be unveiled in September, won't be a true major upgrade but another incremental update of the iPhone 6S, with the major improvements consisting of a new camera, improved 'Plus' model and Lightning port headphone system.
Nikkei is forecasting that a slow down in the smartphone market, coupled with a gradual stagnation in hardware updates, will result in Apple giving itself more breathing room with a three year cycle. Rumours are already suggesting that major updates are planned for the 2017 model, with the return of an all-glass case marking the 10th anniversary of the first iPhone model.
So, if you want a really different iPhone, best try keeping your iPhone 6 working until 2017.