You can get the local timezone offset of the client to get the GMT time and then add the offset hours of the Germany timezone (Central European Time GMT+1):

function getDate(offset){

  var now = new Date();

  var hour = 60*60*1000;

  var min = 60*1000;

  return new Date(now.getTime() + (now.getTimezoneOffset() * min) + (offset * hour));

}



//...



var dateCET = getDate(1); // Central European Time is GMT +1



if (dateCET.getHours() < 12) {

    alert (Good morning.);

} else {

    alert (Good afternoon.);

}

Update: I agree with @Josh, the above code is completely client dependent. Let's try to do it better:

$(document).ready(function(){

  var timezone = Europe/Berlin;

  $.getJSON(http://json-time.appspot.com/time.json?tz=+timezone+&callback=?,

    function(data){

      if (data.hour < 12) {

        alert (Good morning in +timezone);

      } else {

        alert (Good afternoon in +timezone);

      }

    })

});

We are now taking advantage of JSONP to do Cross-Domain requests to the jsontime server, this server exposes a complete JSON API to query time and timezone information.

You can play with the code here and you can explore the JSONP API here.

Hurray!, no server-side code!