If you want to move your event for a few days back or forth - simply drag it from it's current day and drop it on the desired day in calendar. If this is an reminder with a pre-reminder - the pre-reminder will be moved as well.
You can also open the reminder to be rescheduled and change it's start day and/or recurrence options.
For more information about the Main Talking Reminder Window. please Click here.
For more information about modifying existing reminders, please Click here.