+Before you load the library module in your code, you have to uncomment appropriate lines of the library source depending on your Scheme implementation. This is caused by how Scheme implementations provide time related functions: Racket depends on [SRFI-19](http://srfi.schemers.org/srfi-19/srfi-19.html), while Chez Scheme has a subset of those listed in the latter.
Issue `(import (scheme-bert))` in your REPL or put this in head of your source file.
You will also probably want to import some other libraries such as `bytevectors`.
Please, drop me an email if you used or intend to use the library in your project ;-)