Try something like this:
[YOUR BASE SEARCH]
| eval newformat=strftime(strptime(yourtimefield,"Current format of date/time field"),"Format you want the date/time in")
| table yourtimefield newformat
Example with current format and new format:
[YOUR BASE SEARCH]
| eval newformat=strftime(strptime(yourtimefield,"%H:%M:%S.%3q %Z %b %d %Y"),"%m/%d/%Y %p")
| table yourtimefield newformat
To help determine your time format, see Date and Time Format Variables documentation: http://docs.splunk.com/Documentation/Splunk/6.5.3/SearchReference/Commontimeformatvariables
