Board Thread:Questions and Answers/@comment-24263585-20131207182614/@comment-1429792-20131207205157

Akuma Hollow wrote: In some discussions between Arrancars, such as Neliel and Nnoitra, it is stated that the Espada system has existed for some years prior to their discussion. The one who funded the Espada was undoubtadely Aizen, though he only did it after he betrayed and left Soul Society. That means that in the Human World only a few months passed since he went to Hueco Mundo to when he arrived at Karakura town. My point is: is it possible that Hueco Mundo has a similarity to Dangai in terms of their time-density, meaning that one hour in the Human World is equivalent to several more hours in Hueco Mundo?

Aizen was going to Hueco Mundo long before he defected from Soul Society, as evidenced by his recruitment of Baraggan (Tosen had his haori and Aizen had his old hairstyle/glasses, both of which were left behind when they fled SS, placing it prior to the defection) as well as Dordonni's comments about how he knew that the older Espada would become obsolete once Aizen acquired the Hogyoku.