The idea here is to cd into a given directory and then backup a directory in it. The path names are hard coded to make things simple.

#! /usr/bin/env zsh
set -e
topdir=/home/rajulocal/notes
bdir=projects

cd ${topdir}

asof=`date +'%Y%m%d_%H%M%S'`
ofile=${bdir}_${asof}.txz
tar cJf ${ofile} ${bdir}
if [ $? -eq 0 ]; then
    printf "backup stored in: ${topdir}/$ofile\n";
fi

Sample run:

% ~/bin/bkup_notes.sh
backup stored in: /home/rajulocal/notes/projects_20160103_224746.txz