@geerlingguy

$ cat /usr/local/bin/when
#!/bin/bash
if [ -z "$(echo "$1" | egrep "^[0-9]{10,19}$")" ]; then
echo "Usage: $0 epoch" 1>&2
exit 1
fi

t=${1:0:10}
nano=${1:10}

date -d @$t "+%Y-%m-%d %H:%M:%S"