Probably international age. In Korea theres an international age where every one ages by 1 on new years
The representative of the Wolf Kingdom said with a sinister smile, "Cooperate? It's just a year's worth of new lords. Is there a need to make such a big fuss? Even if they are all annihilated, it won't have much of an impact."
Lord Of The People: I Recruited A Mutant Succubus From The Start