User blog comment:Xilinoc/Ch. 664 - The Gift/@comment-25897574-20160228212945/@comment-27001684-20160228233235

They don't seem to be stuck that long (not all at least), Yhwach recruited Äs Nodt in a modern looking hospital and the "Y" twins also seems to be from this era, given the modern looking hospital when they were born.

The captains probably trained their Bankais in a place like the Muken.