To use TrueTime, you must first compile the kernel files. This is done using

>> make_truetime

Since TrueTime is written in C++, you need to have a C++ compiler installed on
your computer, and the mex command must be properly configured to use it. Do

>> mex -setup

to select an appropriate compiler. Gcc works under Linux and Mac OS Microsoft
Visual Studio C++ can be configured to work with mex under Windows (see
Mathworks home page for more help).