User blog comment:Nomimushi/Discussion: Shizuo's Age./@comment-33442125-20171110012308/@comment-26805757-20171110020832

Then he is a year older in the Daily Life arc, because it happens around 4th of may, were Izaya is supoused to turn 24. Or maybe he turned 25...

I think the problem is, Izaya is 23 at the beggining, 24 at the beggining of the second season 2 (around volume 4) and he turns 25 in daily life arc. Because a year certainly didn't pass between Daily Life Arc and Dragon Zombe's, right?