他从学校DROP OUT出来就办公司了，那这个J1从什么时候到什么时候结束的？ J1的定义在下面：

A J-1 visa is a nonimmigrant visa that allows people to participate in exchange programs in the United States that promote cultural and intellectual exchange. The programs are designed to facilitate the exchange of people, knowledge, and skills in the arts, education, and science. 

J-1 visa holders may be:

students, professors, researchers, teachers, au pairs, and specialists. 

J-1 visa holders must:

• Meet eligibility criteria 
• Meet English language requirements 
• Be sponsored by a university, private sector, or government program 
• Obtain specific health insurance coverage 

J-1 visa holders are usually required to return home for two years after their visa expires to share the cultural knowledge they learned in the United States.