normally, the iteration ends on the previous day and the new one starts the next day. for example, our iteration are two weeks span that starts on Apr 15, 2015 and goes to Apr 28, 2015 Close of business. the next day, we do sprint review and sprint planning and start the next sprint on apr 29, 2015 that spans to May 12, 2015.
In some instances, the date/timestamp of your local settings might throw this and the board might show that sprint end and starts on the same day. I would check that as well