Trying to add an internal clock on my App but it's not refreshing the window to change the hours minutes and seconds

I tried placing all my code in a function thinking I will call the function on the text property inside a label but nothing shows up on the label however when I call the variable time on the text label it does display the time but everything stays static on the timelabel in order to see if the time change I have to close out the application and open it again then I can see the minute change I wanted to know how can make this work? I even used setTimeout and setInterval but it only closes the window out var nowDate = new Date(); var nowHour = nowDate.getHours(); var nowMinute = nowDate.getMinutes(); var nowSecond = nowDate.getSeconds(); var amOrPm = nowHour;

if(nowHour>'12'){
    amOrPm ='PM';
}else{
    amOrPm='AM';
};
if(nowMinute<'10'){
    nowMinute ='0'+nowMinute;
};

if(nowSecond<'10'){
    nowSecond='0'+nowSecond;
};

if(nowHour=='18'){
    nowHour='6';
}else if(nowHour =='19'){
    nowHour='7';
}else if(nowHour=='20'){
    nowHour='8';
}else if(nowHour=='21'){
    nowHour='9';
}else if(nowHour=='22'){
    nowHour='10';
}else if(nowHour=='23'){
    nowHour ='11';
}else if(nowHour=='00'){
    nowHour ='12';
        /////////////////////////////
}else if(nowHour=='13'){
    nowHour ='1';
}else if(nowHour=='14'){
    nowHour ='2';
}else if(nowHour=='15'){
    nowHour ='3';
}else if(nowHour=='16'){
    nowHour ='4';
}else if(nowHour=='17'){
    nowHour ='5';
}
var time = nowHour+':'+nowMinute+':'+nowSecond+''+''+''+amOrPm;