For several years now, Germany has some rules concerning fixed-term contracts in academia. Roughly speaking, you can be employed for 6 years after you got your degree in order to work towards your PhD. And then, after obtaining your PhD, you can be employed for another 6 years. In this second part, you should work on your "Habilitation" or, more generally speaking, towards a professorship. Most of the time, people get fixed-term contracts for two or three years (Maybe that's not even true: according to the union GEW, most of the fixed-term contractors in academia are employed for only a few months at a time) and then maybe these contracts will be extended until the 6 years are completed. If you go to another university after having worked towards your (still uncompleted) PhD, let's say for 4 years, you can only work another 2 years at any other university in Germany to complete your PhD. Of course, there are some possibilities to extend these periods when you have kids or when you have to look after your parents and the like.
On the one hand, these rules (especially concerning the first 6 years) could be seen as in favor of PhD students: supervisors know that the PhD student has only 6 year's time and they should support their students to finish their theses within this period. Before this rule applied, some (or most?) PhD students weren't able to finish their theses within a reasonable period; they had so many tasks at the institute that there was almost no time left for their own research. Surprisingly, this habit of exploiting assistants hasn't changed much. The only consequence: PhD students finish their theses while being unemployed, because their 6-years period has finished -- or they emigrate to Switzerland. One could of course argue that this is intended and part of getting a PhD ("Lehrjahre sind keine Herrenjahre" -- you have to pay your dues); young researchers thus face the fact that staying in academia is not easy and they should think carefully about how to proceed their career. You are in your early 30s and there are still many options to get a good job in "the real world," so you benefit from your studies and from having a PhD.
It's worse with the second 6-year period. Maybe you even could extend this time because you have the average 1.39 kids and you even could acquire a grant for yourself, so you stayed 9 or 10 years at university after your PhD -- of course, you had contracts at two or three different universities. But after this? You may be qualified for professorship and maybe you could interview for some positions, but you haven't gotten one yet -- only a very small percentage of all students get a professorship, there still is no tenure system. You cannot stay at your institute, but now being far in your 40s, never having worked outside the Ivory Tower, who will offer you a "real" job in the "real" world? And you face a de facto professional ban in academia -- unless you find one of the rare unlimited positions or you emigrate to Switzerland.
Germany has no real tenure track system, but some years ago, they invented "Junior Professors." You can be a professor without a habilitation, and you can get this professorship after only a very few years after having completed your PhD. Sounds good, right? But the magic 6 years are involved as well.
To acknowledge that people have different educational paths and maybe decided to study after having completed an occupational training and may have worked even some years in their profession, we now have a certain age (i.e., your real age) and an academic age -- the years after a certain degree. So two PhDs can be in their second postdoc year, but one is 29 and the other 39 -- there shouldn't be any discrimination. Usually, with the academic age, you refer to the most recent degree.
But that's not how the rules for Junior Professors work: You can get a junior professorship only within 6 years after you finished your studies and you have to have a PhD and a good publication record, be recognized as researcher in your community, etc. So for me, the moment I finished my PhD, I was too old -- after my studies, I worked for 6 years (yeah! 6!) as e-learning consultant, I got my PhD 10 years after I got my M.A. In Switzerland, the MA is considered the regular degree -- every BA student has the right to enter a MA program, parents are obliged to support their kids until they finish their MA. In Germany, the BA is considered the regular degree -- if you have Abitur, you can enter (almost) every BA program, but to enter a MA program, you have to meet strict criteria. This is obviously a different understanding of the Bologna process, but that's not my point here.
Up to now, the rule "6 years after you finished your studies" refers to the MA degree -- that's what you find as explanation. But when the BA is the "regular degree," this would actually mean that you only can apply for a junior professorship within 6 years after your BA. Which is rather unlikely -- you need two more years for your MA, which you need to be qualified for doing a PhD, for which you need another three years. And when you are a "real" humanities scholar, you probably haven't published anything until then and it will take you three more years to even have your dissertation published in a series of a "recognized" publishing house your supervisor happens to be an editor for.
On the other hand, universities increasingly see this junior professorship as another form of a "senior assistant" -- the position for a postdoc working towards their Habilitation or professorship. And if you look at the salary, that's true. The only difference is that for a regular postdoc position, you have 6 years after your PhD, whereas for the junior professorship, you can apply within 6 years after your first degree.
Brave new world.