Convert human time to epoch, deliver to Zabbix item

Sample line:

echo "line content 12/24/2019"

visudo:

# Defaults        requiretty
zabbix ALL=(ALL) NOPASSWD: /usr/bin/grep expires /path/to/filename

UserParameter:

UserParameter=licence.status,/usr/bin/grep expires /path/to/filename | grep -Eo "....\/..\/.." | awk -F'/' '{ print $2"/"$3"/"$1}' | xargs date +"%s" -d

Define the days in Template/Host level:

{$DAYS_LEFT}=365d

Trigger expression:

{check lincence:licence.status[/path/to/file.dat].last()}-{check lincence:licence.status[/path/to/file.dat].now()}<{$DAYS_LEFT}