This chart shows when players first created their account. Since it's derived from achievements data and achievements first have been introduced in october 2008, all accounts created before that are summed up in one bar.
Interesting enough, roughly half of players created their account and logged in at least once back in 2008 or before. Furthermore, december appears to be the month most people start playing wow.
Now, let's take a look at how many years people play WoW. The data is derived from the achievements "WoW's Xth Anniversary", telling if someone was logged in during the anniversary events. By counting the number of those achievements we can find out how many years someone has played WoW.
Since the first achievement of this series was "WoW's 4th Anniversary", we can only tell if someone played since then. Therefore, we can only count the number of players playing wow for 8 to 11 years, e.g.
The numbers of how many people really played WoW since the beginning without any break may be surprising...