The date and time pickers allow you to enter your search range. Below is an example of a search range:

The call I want to find started on 16th January 2013 at about 10:28.

You could use the following search range:

This range will find all calls on January 16th starting between 10:15:00 and 10:30:59.

When you have entered your search range, click on the "ok" button.