Need info on possible discrepency of Jewish calendar dates

This morning I was led to these two videos before looking at the news.

https://www.youtube.com/watch?v=9g2PutZlwEs

https://www.youtube.com/watch?v=pBhv0gNlyC4

Pay attention to meaning of Donald John Trump!
Sept. 16-17, Yes there is a Full Moon https://www.calendar-12.com/moon_calendar/2016/September
The 3rd day would fall on Sunday.

Anyone here have knowledge or way to find out about this possible calendar change spoken of on the second video regarding Hebrew calendar being off a bit?????
Please discuss in relation to the topic speaker tells about in video.