list-earlier-months.bash

#!/usr/bin/env bash
# vim:filetype=sh:tabstop=4:shiftwidth=4:expandtab:

set -e

start_at_year=2019
start_at_month=1

stop_at_year=2017
stop_at_month=10

y=${start_at_year}
m=${start_at_month}

for y in $(seq ${y} -1 ${stop_at_year}); do
    for m in $(seq ${m} -1 0); do
        if [ ${m} -eq 0 ]; then
            m=12
            break
        fi
        padded_month=$(date --date ${start_at_year}-${m}-1 +%m)
        echo ${y}-${padded_month}
        if [[ ${y} -eq ${stop_at_year} && ${m} -eq ${stop_at_month} ]]; then
            break
        fi
    done
done