Display two fields side by side in a Bootstrap Form

I am trying to display a year range input on a form that has a 2 textboxes. One for the min and one for the max and are separated by a dash.

I want this all on the same line using bootstrap, but I cannot seem to get it to work correctly.

Here's my code:

<form id="Form1" class="form-horizontal" role="form" runat="server">
    <div class="row">
        <div class="form-group">
            <label for="tbxContactPhone" class="col-sm-2 control-label">Year</label>
            <div class="col-sm-4">
                <asp:TextBox ID="TextBox1" CssClass="form-control" runat="server" MaxLength="4" />
            </div>
            <label class="col-sm-2 control-label">-</label>
            <div class="col-sm-4">
                <asp:TextBox ID="TextBox2" CssClass="form-control" runat="server" MaxLength="4" />
            </div>
        </div>
    </div>
</form>

Here's what it looks like now:

How about using an input group to style it on the same line?

Here's the final HTML to use:

<!-- language: lang-html -->

<div class="input-group">
    <input type="text" class="form-control" placeholder="Start"/>
    <span class="input-group-addon">-</span>
    <input type="text" class="form-control" placeholder="End"/>
</div>

Which will look like this:

Here's a Stack Snippet Demo:

<!-- begin snippet: js hide: true --> <!-- language: lang-html -->

<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.css" rel="stylesheet"/>

<div class="input-group">
    <input type="text" class="form-control" placeholder="Start"/>
    <span class="input-group-addon">-</span>
    <input type="text" class="form-control" placeholder="End"/>
</div>

<!-- end snippet -->

I'll leave it as an exercise to the reader to translate it into an asp:textbox element