function calculate_time_zone() {
var rightNow = new Date();
var jan1 = new Date(rightNow.getFullYear(), 0, 1, 0, 0, 0, 0);  // jan 1st
var june1 = new Date(rightNow.getFullYear(), 6, 1, 0, 0, 0, 0); // june 1st
var temp = jan1.toGMTString();
var jan2 = new Date(temp.substring(0, temp.lastIndexOf(" ")-1));
temp = june1.toGMTString();
var june2 = new Date(temp.substring(0, temp.lastIndexOf(" ")-1));
var std_time_offset = (jan1 - jan2) / (1000 * 60 * 60);
var daylight_time_offset = (june1 - june2) / (1000 * 60 * 60);
var dst;
if (std_time_offset == daylight_time_offset) {
dst = "0"; // daylight savings time is NOT observed
} else {
// positive is southern, negative is northern hemisphere
var hemisphere = std_time_offset - daylight_time_offset;
if (hemisphere >= 0)
std_time_offset = daylight_time_offset;
dst = "1"; // daylight savings time is observed
}
var i;
// check just to avoid error messages
if (document.getElementById('timezone_select')) {
for (i = 0; i < document.getElementById('timezone_select').options.length; i++) {
if (document.getElementById('timezone_select').options[i].value == convert(std_time_offset)+","+dst) {
//alert("Timezone="+document.getElementById('timezone_select').options[i].value);
document.getElementById('edit-timezone').value = document.getElementById('timezone_select').options[i].value;
//document.getElementById('edit-timezone').value = '00:00,1';
document.getElementById('timezone_select').selectedIndex = i;
break;
}
}
}
}
function convert(value) {
var hours = parseInt(value);
value -= parseInt(value);
value *= 60;
var mins = parseInt(value);
value -= parseInt(value);
value *= 60;
var secs = parseInt(value);
var display_hours = hours;
// handle GMT case (00:00)
if (hours == 0) {
display_hours = "00";
} else if (hours > 0) {
// add a plus sign and perhaps an extra 0
display_hours = (hours < 10) ? "+0"+hours : "+"+hours;
} else {
// add an extra 0 if needed
display_hours = (hours > -10) ? "-0"+Math.abs(hours) : hours;
}
mins = (mins < 10) ? "0"+mins : mins;
return display_hours+":"+mins;
}