I have made an application in python3.7, with tkinter, when coding is all correct, it works perfectly, but when doing it executable with cx_freeze, in a section of my application where I open a calendar, the error jumps. 
I think you have to add something else to the folder where the executable is, since before reaching this point you should also copy some more files that were not added with when doing the build.
Update: The problem is that with the cx_freeze, it does not copy all the files that it needs, since when the build was created, two .dll "tcl86t.dll" "tk86t.dll" were missing, which are inside the root folder of pythonX.X, and the problem that I have postulated was solved by copying the babel folder of the path "\ Python37 \ Lib \ site-packages \ babel" to the lib folder where the ejcutable was created, thus replacing the existing one that has no files.