I have a button which sets the datepicker to tomorrow using the following code:

<!-- language: lang-js -->
$("#txtDateOfJourney").datepicker({ startDate: '+1d'});

But it's not working.

Here's a demo in fiddle

Any Ideas?

You only pass in the options (as in datepicker({ startDate: '+1d'})) when you're initializing the controller. Since it's already initialized you don't need to do that. Instead you want to use the setDate() method and then pass in <del>the javascript date representation of tomorrow</del> a string representing the relative date like this:

<!-- language: lang-js -->
$('#txtDateOfJourney').datepicker('setDate', "+1d");

Demo in Stack Snippets

<!-- begin snippet: js hide: false --> <!-- language: lang-js -->
$('#btnTomorrow').click(function() {     
  $('#txtDateOfJourney').datepicker('setDate', "+1d");
});
<!-- language: lang-html -->
<link href="//cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.2/css/bootstrap.css" rel="stylesheet"/>
<link href="//cdnjs.cloudflare.com/ajax/libs/bootstrap-datepicker/1.4.0/css/bootstrap-datepicker.css" rel="stylesheet"/>

<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.2/js/bootstrap.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/bootstrap-datepicker/1.4.0/js/bootstrap-datepicker.js"></script>

<input type="text" id="txtDateOfJourney" class="datepicker" />
<button type="button" id="btnTomorrow" class="btn btn-info">Tomorrow</button>
<!-- end snippet -->