j1签证有时间要求吗？
一、J-1 非移民学生/交流访问学者在美国最长可以待多久？ (包括停留时间)
J-1 nonimmigrant student and participant in a cultural exchange program may stay no more than five years. The length of time in the United States must be consistent with the terms of your agreement， which you signed before coming to this country. Some students who have graduated from an accredited U.S. university or college are required by their sponsors to return home for two years after graduation， even though they wish to remain here. You can find out about such requirements when your application form is processed at one of our overseas consular posts. Your sponsor may waive these period restrictions if he or she wants us to let you stay longer. We will only grant extensions once we receive written approval from your sponsor. If you leave the United States while under J status， you cannot return without permission from Immigration or unless you qualify for another type of visa. In general， applicants should apply for an extension of stay not less than thirty days but not more than sixty days prior to the expiration of their current stay. Extensions beyond six months require authorization from the Department of State’s Bureau of Educational and Cultural Affairs.
二、我今年夏天去美国参加一个暑期交流项目，9月份开学，我想咨询一下在赴美前我的DS2019表应该怎样办理及如何申请J1签证？需要带哪些材料去大使馆面签？谢谢！ 我觉得如果你9月入学的话，你可以在4月底5月初把DS2019表格寄到你所要就读的学校让他们给你办。因为学校有固定的日期来整理所有已入学的学生的表格并寄给使馆。这个你应该会收到一封来自学校的信告诉你的。这样你就可以按着那封信上所说的准备其他材料然后去使馆面试了（面试一般都是在广州进行的）。关于材料的问题你可以再问问你中介公司的人或上网查查。不过我觉得最重要的还是面试表现好点就行了~！
三、问：我是交换生，现在美国上高三，明年毕业。请问我毕业后是否还能留在美国？ 如果交换期满要回国后能否再次进入美国学习？ 答：如果你的交换合同期限是8个月以下的短期项目，则你在到期之日必须离开美国，没有延期逗留的合法权利；如果合同期限超过8个月，你需要得到移民局批准才能延期居留，但必须符合一定的资格条件：
a. 你必须在原留学单位继续学习，不能转学或换学校;
b. 在校学习时间不得超过合同有效期；
c. 必须在入境时向海关出示有效的I-94卡和有效的F、M、J类学生签证，并在有效期内出入境； d. 必须在入境美国时有足够的资金维持在校学习和生活等必要开支； e. 除上述条件外，还须符合美国移民法规定的其他资格要求。