calculate user's local time as certain GMT times are selected from a drop down box

Posted on 2004-10-09
Last Modified: 2008-03-06
Hi experts,

I am looking for a way to calculate on-the-fly the user's local time as certain GMT times are selected from a drop down box as follows:

<select><option>0:00</option><option>0:30</option> etc </select>

As an input argument to the javascript function that would do this would be the zone offset calculated via  
var curDateTime = new Date()
var myVal = -curDateTime.getTimezoneOffset()/60

from an earlier script.  So as he selects different GMT times, his local time appears beside his choice and updates as he selects different GMT times.

Question by:kesea
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Author Comment

ID: 12268333
Just to clarify, I don't need help with the math part - I would just output the hour selected + the zone offset followed by the minutes.  What I don't know how to do is output this result beside the drop box and have it change on-the-fly as different options are selected from the drop box.
LVL 15

Accepted Solution

Colosseo earned 500 total points
ID: 12268400
Hi kesea

I have created an example webpage for you.

All you will have to do is add your math in to the function to complete it.

Right now it passes the option selected in the drop down to the javascript function and then displays the results to the page.

The function is also called in the onload of the body so that an initial value is generated for the local time but this is not required if you don't want it to do that.

<script language="javascript">

  // This function uses the passed GMT time to calculate the user's local time
  function calcLocalTime(GMT)
    //Variable to hold the local time
    var localTime;

    // Set the local time to the passed GMT value as an example so code works just now
    // This is where you would implement your code
    localTime = GMT;

    // Output the users local time
    document.all.localTime.innerHTML = localTime;

<body onload="calcLocalTime(document.all.selGMT.value);">

<select name="selGMT" onChange="calcLocalTime(this.value);">
  <option value="0:00">0:00</option>
  <option value="0:30">0:30</option>

The user's local time is: <span name="localTime" id="localTime"></span


Hope thats of use, any problems/questions then just let me know




Author Comment

ID: 12268571
Just what I needed.  Thank-you very much.
LVL 15

Expert Comment

ID: 12268583
your very welcome and thanks for the grade



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