A Jiva perceives the length of a day in the higher domain to be 365 days long. A year in the earth plane is equivalent to one day in the realm of ancestors per Vedic texts. Vedic texts also say that the psyche takes some time to adjust to the new length of the day in the higher realm. The transition happens over twelve lunar months. This is like our body adjusting gradually to a new time zone during Jetlag.
Purana texts describe the abstrat idea of the slow transition as an year long journey through the realm of Yama, the Deva of death. A Jiva crosses twleve milestones, one each in 29.5 human days. In, adddition it crosses four important mini milestones which are at 27, 40, 170 and 340 day markers from the time of its exit from its body. A Jiva uses these milestones as an opportunity to release unwanted impressions related to its earlier birth from its psyche through dream like experiences. A son or a daughter performs rituals to a departed soul at these milestones to strengthen the "spirit" of the JIva. These rituals allow the Jiva to get its psyche totally ready for its next assignement in the material domain.