My Javascript and JQuery skills are poor at best and this is **

I have the following three elements in a form :

<select name="event_time_start_hours">
    <option value="blank" disabled="disabled">Hours</option>
    <option value="blank" disabled="disabled">&nbsp;</option>
    <option value="01">1</option>
    <option value="02">2</option>
    <option value="03">3</option>
    <option value="04">4</option>
    <option value="05">5</option>
    <option value="06">6</option>
    <option value="07">7</option>
    <option value="08">8</option>
    <option value="09">9</option>
    <option value="10">10</option>
    <option value="11">11</option>
    <option value="12">12</option>
    <option value="midnight">Midnight</option>
    <option value="midday">Midday</option>
</select>
<select name="event_time_start_minutes">
    <option value="blank" disabled="disabled">Minutes</option>
    <option value="blank" disabled="disabled">&nbsp;</option>
    <option value="00">00</option>
    <option value="15">15</option>
    <option value="30">30</option>
    <option value="45">45</option>
</select>
<select name="event_time_start_ampm">
    <option value="blank" disabled="disabled">AM / PM</option>
    <option value="blank" disabled="disabled">&nbsp;</option>
    <option value="am">AM</option>
    <option value="pm">PM</option>
</select>

Quite simply, when either 'midnight' or 'midday' is selected in "event_time_start_hours", I want the values of "event_time_start_minutes" and "event_time_start_ampm" to change to "00" and "am" respectively.

My VERY poor piece of Javascript says this so far :

$(document).ready(function() {
    $('#event_time_start_hours').change(function() {
        if($('#event_time_start_hours').val('midnight')) {
        $('#event_time_start_minutes').val('00');
        }
    });
});

... and whilst I'm not terribly surprised it doesn't work, I'm at a loss as to what to do next.

I want to do this purely for visual reasons for the user as when the form submits I ignore the "minutes" and "am/pm". I'm trying to decide whether it would be best to change the selected values, change the selected values and then disable the element or hide them altogether. However, without any success in getting anything to happen at all I haven't been able to try the different approaches to see what feels right.

I've ruled out the obvious things like a duplicate element ID or simply not linking to JQuery.

Thank you.