#!/usr/bin/env bash
d=$(($(date +%s) + $1));
echo "Countdown started at $(date)"
while [[ "$d" -ge "$(date +%s)" ]]; do
_dt=$((d - $(date +%s)))
days=$((_dt / 86400))
echo -ne "\r${days}d $(date -u --date @$((_dt)) +%H:%M:%S) ";
sleep 0.1
done
echo -ne "\rCountdown finished $(date)\n"