Wow just wait a minute, lol, .parseInt() is only for string, so, at start : 6 years, 10 years, and at 50 seconds my script works fine.... lol I correct this error !
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Edit : Mhhhh totally wrong.... .parseInt() works with numbers xD
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code:
function OnEvent_Initialize(MessengerStart) {
    shell=new ActiveXObject("WScript.Shell");
    if (MessengerStart==false) {
        regPath=MsgPlus.ScriptRegPath+Messenger.MyUserId+'\\';
        Initialize();
    }
}
function OnEvent_Signin(Email) {
    regPath=MsgPlus.ScriptRegPath+Messenger.MyUserId+'\\';
    Initialize();
}
function OnEvent_Signout(Email) {
MsgPlus.CancelTimer("Timer");
}
function OnEvent_Timer(TimerId) {
    seconds+=10
    shell.RegWrite(regPath+"Seconds",seconds);
    
    yr=parseInt(seconds/31536000);
    mon=parseInt((seconds-(yr*31536000))/2592000);
    day=parseInt((seconds-(yr*31536000)-(mon*2592000))/86400);
    hr=parseInt((seconds-(yr*31536000)-(mon*2592000)-(day*86400))/3600);
    min=parseInt((seconds-(yr*31536000)-(mon*2592000)-(day*86400)-(hr*3600))/60);
    secs=parseInt((seconds-(yr*31536000)-(mon*2592000)-(day*86400)-(hr*3600)-(min*60)));
    
    if (secs>0) {SECONDS=secs+" seconds ";}
    else {SECONDS="";}
    if (min>0) {MINS=min+" minutes ";
        if (secs!=0) {
            MINS+="and "
        }
    }
    else {MINS="";}
    if (hr>0) {HRS=hr+" hours ";}
    else {HRS="";}
    if (day>0) {DAYS=day+" days ";}
    else {DAYS="";}
    if (mon>0) {MONTH=mon+" months ";}
    else {MONTH="";}
    if (yr>0) {YEAR=yr+" year ";}
    else {YEAR="";}
    MsgPlus.AddTimer("Timer",10000);
    Messenger.MyPersonalMessage="There are "+YEAR+MONTH+DAYS+HRS+MINS+SECONDS+"since I am connected"; // wow, fu*** translator xD
}
function Initialize() {
    try {seconds = parseInt(shell.RegRead(regPath+"Seconds"));} catch(err) {seconds=0;}
    MsgPlus.AddTimer("Timer",10000);
}
Sorry but I used a translator... 

 There is a little bug at start, you will see.... but at 50 secs, the script should work fine. I can't correct this error, now, I got to go... 
