Timezone option values

Question

javascript:

function calcTime(offset)

{

d = new Date();

utc = d.getTime() + (d.getTimezoneOffset() * 60000);

nd = new Date(utc + (3600000*offset));

document.getElementById('result').value=nd.toLocaleString();

}

Html:

<select name="timezone" onchange="calcTime(this.value)" >

<option selected>Select Time Zone</option>

<option value="-8">Pacific Standard Time (PST)</option>

<option value="-7" > Mountain Standard Time (MST)</option>

<option value="-6" >Central Standard Time (CST)</option>

<option value="-5"  >Eastern Standard Time (EST)</option>

</select>

 

<input type="text"  id="result"> 

This works on value change... but i want to save value as

<select name="timezone" onchange="calcTime(this.value)" >

<option selected>Select Time Zone</option>

<option value="PST">Pacific Standard Time (PST)</option>

<option value="MST" > Mountain Standard Time (MST)</option>

<option value="CST" >Central Standard Time (CST)</option>

<option value="EST" >Eastern Standard Time (EST)</option>

</select>

 

 but the it is not working if i write PST etc.. What can i do??

Please help