#!/bin/bash printf -v date '%(%Y-%m-%d)T\n' -1 echo $(( ($(date -d $1 +%s) - $(date -d $date +%s)) / 86400 )) days
Above is a bash script to output the number of days between today and some future date. Copy it into a file, e.g., diffdate.sh, into a directory, e.g., ~/bin/scripts. Then, enter the directory you saved it to and type to make it executable:
$ chmod +x diffdate.sh
Then, check your .profile to make sure something like this in it:
# set PATH so it includes user's private bin if it exists if [ -d "$HOME/bin" ] ; then PATH="$HOME/bin:$PATH" fi
Then, run the script.
$ diffdate.sh 2021-06-01 70 days
I have to figure out the difference between today and some future date all the time for forecasting, and today was the day I finally bothered to figure out how to do it from the command line. I have to start thinking of ways to make shell scripts to do this little tasks that I go to the web for.