tell me where the date is calculated from this code:
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">

<script type="text/javascript">
const ponCerosIzq=(e,o=4)=>`${"0".repeat(Math.max(0,o-e.length))}${e}`,pasarMayusculas=e=>e.toUpperCase(),aleatorio=(e,o)=>Math.floor(Math.random()*(o-e))+e,cogeBit=(e,o)=>e.charAt(o),ponBit=(e,o,a)=>o>=e.length?e:`${e.slice(0,o)}${a}${e.slice(o+1)}`,Hex2Dec=e=>parseInt(`0x${e}`,16),Bin2Dec=e=>parseInt(e,2),Dec2Bin=e=>e<1?"":`${Dec2Bin(Math.floor(e/2))}${e%2}`,Hex2Bin=e=>e.replace(/\s/g,"").split("").map(e=>ponCerosIzq(Math.base(e,2,16),4)).join(" "),Bin2Hex=e=>e.replace(/\s/g,"").match(/\d{4}/g).map(e=>parseInt(e,2).toString(16)).join("").toUpperCase();Math.base=(e,o,a)=>parseInt(e,a||10).toString(o);
function arrange_crc(t){var n=cogeBit(t,0);cogeBit(t,8);let r="0",c="0";return c="0"===n?"1":r="0",ponBit(ponBit(t,8,c),0,r)}
function calculaCRC(r){for(var a=r.substring(3,187).split(""),i="00000000".split(""),n=0;n<8;n++){for(var o=0,t=n;t<184;t+=8)o=a[t]^o;i[n]=o}for(var f=0,n=0;n<8;n++)f=i[n]^f;return i.join("")+f}
function creaCodigo(){var ciutat=document.getElementById('cCiudad').value;var tarja=document.getElementById('cTarjeta').value;var zones=document.getElementById('cZones').value;var viatges=document.getElementById('cNViajes').value;var caducidadAny=document.getElementById('caducidadAny').value;var caducidadMes=document.getElementById('caducidadMes').value;var caducidadDia=document.getElementByI Your response should contain 100+ words.
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