If I remember correctly it was a few months but I haven't played that game in over a year so I may be remembering it wrong. a few months sounds accurate but when you think about it the twins were soul reapers in the 5th division and before the fight that forced seigen,fujimaru,arturo,and matsuri you can remember that the twins knew toshiro,momo,gin,rangiku,rukia,Soi Fon and renji and by the time you get to the future which is technically present time for say the show or the arc depending upon how you look at it all of the above were soul reapers(and Soi Fon a Captain) and a little later the twin you are finds out about Aizen and Co's revolt. so a few months sounds accurate since soul reapers age in appearance 1 year for every so many human years its safe to say it could've been longer i do