How to change "to" to "-" while displaying start and end date in views?
My answers assume I have a field called "field_event_date" which shows as Content: Event Date in my view.

Answer #1 - Use View Template


Under the Advanced Section of the view, under the Other section, open Theme Information
Copy the filename of the last theme option for Field Content: Event Date, in my case it will be views-view-field--VIEWMACHINENAME--BLOCKMACHINENAME--field-event-date.tpl.php
Copy the following into it:

&lt;?php

/**
 * @file
 * This template is used to print a single field in a view.
 *
 * It is not actually used in default Views, as this is registered as a theme
 * function which has better performance. For single overrides, the template is
 * perfectly okay.
 *
 * Variables available:
 * - $view: The view object
 * - $field: The field handler object that can process the input
 * - $row: The raw SQL result that can be used
 * - $output: The processed output that will normally be used.
 *
 * When fetching output from the $row, this construct should be used:
 * $data = $row-&gt;{$field-&gt;field_alias}
 *
 * The above will guarantee that you'll always get the correct data,
 * regardless of any changes in the aliasing that might happen if
 * the view is modified.
 */
?&gt;

&lt;?php print date("Y-m-d H:i:s", strtotime($row-&gt;field_field_event_date[0]["raw"]["value"])); ?&gt;
 - 
&lt;?php print date("Y-m-d H:i:s", strtotime($row-&gt;field_field_event_date[0]["raw"]["value2"])); ?&gt;



This will output something like 2014-08-09 20:15:00 - 
2014-08-12 20:15:00, format using the date() format string.

Answer #2 - Use View Fields


Under Fields, add Content: Event Date and set the Display to "Start Date Only"
Under Fields, add Global: Custom Text and set Text to  - 
Under Fields, add Content: Event Date and set the Display to "End Date Only"
Under Field Settings, Set the three fields above as Inline.


This will output something like Sunday, December 1, 2013 - 12:00 - Sunday, December 1, 2013 - 12:00, based on the format you have chosen.