I may not be completely correct but in Chapter 407-408, Isshin explains how outside the Dangai, time moves more slowly than it does inside of the Dangai-by 2000x actually. So even though time seems to have passed by really slowly outside, with time compressed in the Dangai, time is moving really fast for them. So pretty much the 2 month limit is getting really close even though its been what, several minutes in the real world place? It's kind of confusing but in the end, it makes sense. Kind of. Just know that sense time is majorly compressed in the Dangai, it makes time in there go by incredibly fast compared to the outside world. Example: 1 second here is about 33.3 minutes in there.