http://bbs.chinaunix.net/forum/viewtopic.php?t=581267&show_type=
"2004.05.23" 和 "2005.03.01"
date -d `echo "2005.03.01"|tr '.' '-'` +%s [[ "2006.01.23" > "2005.03.01" ]] && echo dayu || echo budayu
[ "2006.01.23" \> "2005.03.01" ] && echo dayu || echo budayu