You can easily reschedule events. If you reschedule a recurring event, you'll be asked if you want to change all occurrences of the event, or just the event you dragged or clicked.
To reschedule an event:
Do one of the following:
Drag the event to the preferred time.
You can drag timed events in the day or week calendar views. You can drag all-day events in the week or month views.
Click the event and change the "start time" and "end time" fields, or click the date and in the calendar that appears, click a date.