In many legislations throughout the world, the act of intentionally killing a person had varied legal consequences, depending on the circumstances. For example, a person planning to kill their neighbor in what is supposed to look like an accident would be different than a fight escalating and leading to the death of one of the people involved.
One distinguishing factor between "murder" and "manslaughter" is whether or not there was premeditation, meaning the perpetrator made the decision to kill someone before it occurred. However, I wonder, how long before the actual killing does this decision need to be made for it to be considered "murder" as opposed to "manslaughter"?
Note: I am mostly interested in answers regarding laws in Europe, but answers regarding other jurisdictions are welcome as well.