credit: https://community.checkpoint.com/t5/user/viewprofilepage/user-id/15143

script_change_expiration_of_selected_user.sh

#!/bin/bash
# Created by tvobruba
# version 001
# script is checking and changing expiration date for internal specific users in CP MGMT database
# usage: chmod 700 && ./script.sh <username>

user=$1
date=1609459162000 #setup checked date in ms epoch time
new_date="2035-01-15" #setup new desired date in ISO format


echo "Checking date/time of expired users..."
echo -e "";

expiration=`mgmt_cli -r true show user name "$user" --format json |jq '."expiration-date".posix'`
echo User: $user, $expiration
echo ""

if [ $date \> $expiration ];
then
    echo "$user will expire before 31.12.2020 23:55";
        echo "Setting new expiration date..."
        echo ""
        mgmt_cli -r true  set user name "$user"  expiration-date "$new_date"  --format json
else
    echo "$user will expire not before: `date -d @$(  echo "($expiration + 500) / 1000" | bc)`";
fi;