The code at https://jodavaho.io/posts/bash-journalling.html doesn't work for me. It looks like it is passing vim the -d args, which doesn't seem right since -d opens a diff view. I think you misplaced a comma for the date command. I fixed it for me by doing like this:

  function journal() {
    vim $logdir/$(date +%Y-%m-%d -d "$\*")
  }