- Changed `\@dtm@year` to `\the\year` LaTeX internal value instead of
datetime2's one
- Commented the requirement of package `datetime2`

- LaTeX compilers prioritizes files containing a `\documentclass`.
  Because of that, it will bug if the root document it's not defined.
  The easiest solution it's just to include it inside the main
  document. In this case, wif.tex.