Dates  with different format are compared

siteStartDate and siteEndDate are in different formats to be compared with startDate and endDate variables.
Test Case: 
Go to the form TimeLineForm.inc.php (index.php/conf/someschedconf/manager/timeline) and setup a conference schedule to siteStart equals 2014-6-1, siteEndDate  equals 2014-9-30, startDate equals 2014-09-12 and endDate equals 2014-09-13. Save it. Check the table 'sched_confs' and verify that all is Okay for siteEndDate value. It's 2014-9-30 as expected. Now, go back to the same schedule conference form and check again their value, it's 2014-09-14! That's the bug.
Merge pull request #11 from dany-eudes/master

*8861* Dates  with different format are compared