Previous dating was based largely upon pottery trends and seriation, as originally devised by Petrie. This can, however, be problematic mainly because of its subjectiveness.
To put it in a nutshell, the data show that the Predynastic period (i.e. when Egypt’s inhabitants moved from a nomadic life to a more sedentary, agricultural life) began around 3700–3800 BCE, rather than c.4000 BCE, as previously estimated. As King Aha, the first king of Egypt, came to the throne in a newly united Egypt around 3100 BCE, this puts the entire period at 600–700 years long. This is considered a relatively short period of time for such a change to occur (and shortening our current chronology of the period by 200–300 years).
The research has also provided a much more reliable absolute chronology for the first eight rulers of the 1st Dynasty.
This new dating appears to give King Djer a particularly long reign, anywhere from 20–50 years to upwards of 150 years (as shown in the photo above, taken from the article). We don’t know why this is, but the article states that:
Djer’s tomb is the largest at Umm el-Qaab, comprising some 318 subsidiary burials; hence the most parsimonious explanation may be that his reign lasted upwards of 50 years. However, the length of this interval could also be the result of a political hiatus or some other missing archaeological information.
You can read the full Royal Society article here, though do beware that it is a science-based article; I couldn’t quite understand the sections about their scientific methodology because that’s not my expertise. If you want to skip to the less-sciency bit, go straight to section 4 (Model Outputs and Discussion).
Other articles are available here:
(PS Don’t bother with the Daily Mail article. As usual, they’ve got their facts a bit mixed up!)