User blog comment:Kallutofan990/Why does Killua's age say his 14 currently?/@comment-4932025-20131107155415

Gon is older than Killua?, Gon's birthday is on May 5th while Killua's is on July 7th, Well they're both 13 during the Yorknew City arc that's for sure (September 1st - 4th)

When Killua left G.I to return to the real world it was December 29th 1999(I assume the Hunter exam is on January), After this there's just speculation. I highly doubt he's 14, the ant arc + election arc weren't that long imo. Now if only we could get the date of the 13th chairman election that'd be great.