我去年I-797 Approval notice 的 valid from 9/1/2015 to 8/31/2016，去年回国拿到签证，护照上issue date 8/20/2015,expiration date 8/18/2016,进入海关,给我的入境停留时间是8/18/2016.因此,今年的offer letter 从8/18/2016 to 8/17/2017.
今年学校帮我在美国延期，新的I-797 Approval notice 的 valid from 9/1/2016 to 8/31/2017，不是从8/18/2016开始。
我的问题：
1.8/18/2016 到9/1/2016 我是否属于合法居留，如何不属于，如何处理？
-You need to check your I-94 expiration date at:
If your I-94 expiration date was also 8/18/2016, then your presence was unlawyful from 8/19/2016 to 8/31/2016. Thus, you had better go to the local CBP Deferred Inspection Office to see whether they can fix it for you. Bring your old H-1 approval notice and your passport, and the I-94 (print it out at above website). Otherwise, techincally you may need to go to China to get the H-1 visa to come back. However, because you have a new H-1 approval and a new I-94, you may not need to go to China immediately, and may go any time later. Also because the unlawful presence is very short, it should not affect you much.
Find the CBP Deferred Office in yoiur area here:
If the old H-1 I-94 expiratio date was 8/31/2016 or 9/10/2016, then you are OK and do nothing.
2.我儿子是H4，因为6月份回国，7月份回来，入境停留的时间截止到9/20/2016，和我一起延期，新的I-797 Approval notice 也是 valid from 9/1/2016 to 8/31/2017，和我一样，如果我居留不合法，他是否也是不合法？如何处理？
-Do the same way as you (see my suggestion above).
谢谢
