Simple mathematicall formula???

You could use the Date object for it. See <uri:http://developer.mozilla.org/en/docs/Core_JavaScript_1.5_Reference:Global_Objects:Date> for data about that.

I'm glad njwoods asked this question. Was just about to ask about time differences and there was a good example in the link from liorean.

I'm having problems using a function to update the time. Am I missing something simple or does this have to do with the date/time requirements?

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<script type="text/javascript">

var timeA = new Date();
var timeB = new Date();
var timeDif = timeB - timeA;

function UpdateTimeB(){
timeB = new Date();
}

</script>

<input type="button" value="timeA" onclick="alert(timeA)"><br><br>
<input type="button" value="timeB" onclick="alert(timeB)"><br><br>
<input type="button" value="timeDif" onclick="alert(timeDif)"><br><br>
<input type="button" value="UpdateTimeB" onclick="updateTimeB()"><br><br>

swtrans:
You did the timeDif=timeB-timeA part once, with the original values for timeA and timeB. You never after that update timeDif, so it will stay the same. Only timeB will be updated.

liorean see what you mean. I added an update to that, but for some reason I keep getting an error when I push the update button.

<script type="text/javascript">

var timeA = new Date();
var timeB = new Date();
var timeDif = timeB - timeA;

function UpdateTimeB(){
timeB = new Date();
timeDif = timeB - timeA;
}

</script>

<input type="button" value="timeA" onclick="alert(timeA)"><br><br>
<input type="button" value="timeB" onclick="alert(timeB)"><br><br>
<input type="button" value="timeDif" onclick="alert(timeDif)"><br><br>
<input type="button" value="UpdateTimeB" onclick="updateTimeB()"><br><br>

I see the problem:

onclick="updateTimeB()"

case sensative

onclick="UpdateTimeB()"><