[javascript] subtract time from date - moment js

I might be missing something in your question here... but from what I can gather, by using the subtract method this should be what you're looking to do:

var timeStr = "00:03:15";
    timeStr = timeStr.split(':');

var h = timeStr[1],
    m = timeStr[2];

var newTime = moment("01:20:00 06-26-2014")
    .subtract({'hours': h, 'minutes': m})
    .format('hh:mm');

var str = h + " hours and " + m + " minutes earlier: " + newTime;

console.log(str); // 3 hours and 15 minutes earlier: 10:05

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$(document).ready(function(){    _x000D_
     var timeStr = "00:03:15";_x000D_
        timeStr = timeStr.split(':');_x000D_
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    var h = timeStr[1],_x000D_
        m = timeStr[2];_x000D_
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    var newTime = moment("01:20:00 06-26-2014")_x000D_
        .subtract({'hours': h, 'minutes': m})_x000D_
        .format('hh:mm');_x000D_
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    var str = h + " hours and " + m + " minutes earlier: " + newTime;_x000D_
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    $('#new-time').html(str);_x000D_
})
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<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.9.0/moment.min.js"></script>_x000D_
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<p id="new-time"></p>
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