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Yes, you can, read more in http://splunk-base.splunk.com/answers/11649/specify-timestamp-display-format-for-timechart-axis-labels?page=1&focusedAnswerId=11652#11652
For me, Ron Naken tip worked.
Read this for more about date format info: http://docs.splunk.com/Documentation/Splunk/5.0.1/SearchReference/Commontimeformatvariables
Use something like above to get your "3/12/Sat" format:
... | rename _time AS Time | eval Time=strftime(Time, "%m/%d/%A")
I hope this can help you!