When is Zakat due on a deceased person's cash and in-kind assets, which have not yet been divided among the heirs, given that the last time Zakat was paid is unknown?

If a person dies, their money and rights are transferred to their heirs. If the obligation of Zakat on their wealth was not clear before their death, then there is no Zakat on it. Each heir must then start a new lunar year with their share, and pay Zakat on it if it reaches the nisab and a full year passes over it.