I am using this calendar for a reservation system for lodging. I have a "Check In" and "Check Out" date in a mysql database. Currently when I connect the database to the calendar it shows the "Check Out" date as booked/unavailable. I have tried using php to minus one day from the checkout date since a guest could book the same day someone is checking out but will not work with common php commands. How can I minus a day from a date that is in the mysql database when loading on the calendar?

For anyone who are looking to change the dates on the calendar here is the code that works.
<?php echo dmxCalendarFormat(date('Y-m-d',strtotime ( '-1 day' , strtotime ( $row_CabinCalendar['DateStop']))), "yy-mm-dd" ; ?>