It cannot.

What can be dated is healing, and healing happens on a schedule that is reasonably well described, and the schedule is a range and not a point.

For the femur.

A transverse fracture of the femoral shaft in an infant causes immediate, severe, unmistakable pain.

It is not an injury a child sleeps through and it is not an injury that announces itself two days later.

A fracture like that produces a scream at the moment it occurs, and then a period of distress, and then a baby who is inconsolable when the limb is moved and relatively settled when it is not.