User blog comment:Zaarqawi/Why players from YGGDRASIL have been transported to the New World at various periods of time./@comment-27131588-20151108142213

For some reason it depends on their coordinates during the end of game

For example: Momonga was in Nazarick during the end and he got sucked with GToN in the"present"

However, in side story about Momonga and Evileye, he decided to make fireworks to go with bang and he got sucked into 13 Heroes era (approximately, cuz he got sucked into ruined city where Evileye resided before her joining the heroes)