Max function not working on import range in google spreadsheet

Question

I am new to google spreadsheet functions and trying to apply formula in following way:

I have an imported range as under in cell B2:

=importrange("1gRRBtq7KMAr5kY5AJBqFcLarkikqrAqr5CbeTc5mPzE/edit#gid","dstr!b2:b400")

This range contains different dates & I am trying to select last date with following function in B1:

=max(B2:B398)

But in place of showing date it is showing value.

Please help in solving this concern, for more detail you can go to following page:

https://docs.google.com/spreadsheets/d/1HTXf4VG2JupiP9UqCLRyAddYjhsom1leQOI9-DwfMaY/edit#gid=0

Answer 1

I selected cell B1 and clicked on the 123-button (in the menubar) and formatted that cell as date. See if that helps ?