cal() {
    local CURR_DAY_OF_MONTH CURR_MONTH_YEAR GRAD_MONTH_YEAR COLOR DECORATED_TEXT
    local IFS='%'

    CURR_DAY_OF_MONTH="$(date +%e)"
    CURR_MONTH_YEAR="$(date +%b\ %Y)"
    GRAD_MONTH_YEAR="$(for COLOR in {17..21} 0 {21..17}; do [ "$COLOR" -eq 0 ] && DECORATED_TEXT="\e[7;49;33m ${CURR_MONTH_YEAR} \e[0m" || DECORATED_TEXT=" "; printf "\e[48;5;${COLOR}m${DECORATED_TEXT}\e[0m"; done)"

    case "$(uname)" in
        Darwin)
        CAL_OPTS="-h"
        ;;
        Linux)
        CAL_OPTS=""
        ;;
    esac

    [ -z "$1" ] \
        && printf \
        "$(/usr/bin/cal ${CAL_OPTS} \
        | sed -r -e 's/(^.* '${CURR_MONTH_YEAR}' .*$)/'${GRAD_MONTH_YEAR}'/g;s/(^.* )('${CURR_DAY_OF_MONTH// /\\ }')(.*$)/\\e[7;49;37m\1\\e[7;49;91m\2\\e[0m\\e[7;49;37m\3\\e[0m/g')\n" \
        || /usr/bin/cal $*

    unset IFS
}