Loop with date (MAC)

dateloop.sh

#!/bin/bash

# On MAC date -d option does not work rather -v.
# Below code logic is as follows:
# Create folders with date(in format YYYY-MM-DD) with consecutive dates until it reaches to input difference
# Here variable datediff is 28 meaning from current date, it will generate dates until there is difference of 28.

now=$(date -v  -1d +"%Y-%m-%d")
datediff=28
for (( c=0; c<=$datediff; c++ ))
do
    echo $c;
    now=(`date -v  -"$c"d +"%Y-%m-%d"`);
    mkdir /tmp/"$now"
done