#!/bin/bash
echo something 1989-07-23 something.jpg foo-2013-01-10-bar.csv wordsidon\'tcareabout_2004-09-14_otherthings.tif foofoobarbar_2010-07-16.gif | grep -Po '(?<=\D)\d{4}(.\d\d){2}(?=\D)'
IyEvYmluL2Jhc2gKCgplY2hvIHNvbWV0aGluZyAxOTg5LTA3LTIzIHNvbWV0aGluZy5qcGcgZm9vLTIwMTMtMDEtMTAtYmFyLmNzdiB3b3Jkc2lkb25cJ3RjYXJlYWJvdXRfMjAwNC0wOS0xNF9vdGhlcnRoaW5ncy50aWYgZm9vZm9vYmFyYmFyXzIwMTAtMDctMTYuZ2lmIHwgZ3JlcCAtUG8gJyg/PD1cRClcZHs0fSguXGRcZCl7Mn0oPz1cRCknCg==