User blog comment:Martialmaniac/HxH timeline/@comment-26871067-20161216042007/@comment-5780397-20161216100137

Ok, now it is a bureaucratic issue. I think MrGenial11's last reply to the sub-discussion started by Hiatusxhiatus2 is a good way to avoid reading through all the rest.

I too thought this could be material for the Trivia section, but since we have listed multiple ages for some characters (e.g. how old Gon was during his debut and how hold he is now), and since we have used the age section to indicate Maha's age had been retconned, I think it's only fair we bring it up there.

Saying Gon's official age is 12 actually is presumed knwledge. The Hunter Election started on August 8th (date stated in chapter 320), and he was said to be 12 around that time. The Black Whale left harbour on August 8th of the following year (date stated in chapter 349, and it departs in chapter 359). Unless all the rounds of the election, the Hunter Exam, Kakin's announcement etc. have taken place in a few hours, a year must have passed, so it's impossible for Gon to be still 12. So the most accurate piece of info would be that officially, Gon was 12 during the Hunter Election arc.