Other Issues: How Can I Calculate the Two Years Home Residency to Fulfill the Condition

I came to USA in January 17th 2003 to do my Ph.D. with J-1 visa. I stayed for 9 years with this J-1 visa. I finished my Ph.D. and stayed for the academic training during these 9 years. I left USA in January 9th 2012 and changed my visa to J-2 visa because my wife was still doing her Ph.D. I back to USA in February 4th 2012. I stayed another three years with the J-2 visa. I visited my home country for three months during these three years.
I want to know if these three months counted from the 24 months required from the J-1 visa holder.

I left with my family in July 10th 2015 and stayed in the country of origin till February 10th 2017. During that time my wife received a waiver from the two years home residency of her J-1 visa (my J-2 visa too).

I want to know How can I calculate the two years home residency to fulfill the condition?

Other Issues: How Can I Calculate the Two Years Home Residency to Fulfill the Condition