How to prevent screen lock when MacBook AC adapter is unplugged?

You can't add a new horse type without modding the game, you can just edit it using resource packs (like you did).

You could do it in 2 date operations. Here's a quick bash shell script:

TIME_TEN_MINUTES_AGO=`date -d '-10 min' +%T`

LAST_MON=`date -d 'last-monday' +%Y-%m-%d`

echo "NOW:      " `date "+%Y-%m-%d %T"`
echo "Last Mon: " $LAST_MON $TIME_TEN_MINUTES_AGO

This prints:

NOW:       2016-02-12 07:54:27
Last Mon:  2016-02-08 07:44:27