Why does turbotax tell me that September 2018 is not within the tax year?

We're attempting to file a trust return and had two stock sales.  One of those was made on April 16 2018.  During the review process this keeps coming up as not within the tax year, and I can't seem to get the program to accept it so we can file.

April or September? You said both.

April

Would you mind providing a bit more context? What were you attempting to do when you saw this message?  Also what did the error say exactly?

We're attempting to file a trust return and had two stock sales.  One of those was made on April 16 2018.  During the review process this keeps coming up as not within the tax year, and I can't seem to get the program to accept it so we can file.