Prosecutors said they would have recommended a harsher sentence for Yeo, who pleaded guilty to acting as an agent of a foreign government, but for his cooperation.
At the time, such changes were considered controversial, but not nearly as controversial as the plan to put the calendar back into sync with the seasons.
The United States first intervened in Afghanistan following the September 11, 2001 attacks and dislodged the Taliban regime, which had welcomed Al-Qaeda.
At least 15 people were killed and 42 others got injured in a car bombing outside a district office in Afghanistan's eastern Nangarhar province on Saturday.