A more thorough explanation:

Simultaneous death acts are laws that apply when two people die within a short amount of time. These laws change how assets are distributed when someone dies without a will. The laws treat the deaths as if each person died before the other.

For example, if a husband and wife die in a car accident, the law would act as though each died before the other, even though that is impossible. This is important because it changes how their assets are distributed.

The length of time that people are considered to die simultaneously differs by state, but 21 states and D.C. have adopted the 120 hours limit from the Uniform Simultaneous Death Act.

Overall, simultaneous death acts help ensure that assets are distributed fairly when two people die at the same time.