You can change the interval of a repeating item as needed.
In your calendar, open the appointment or meeting you want to change. Select Edit Series, and then click OK.
On the appointment or meeting toolbar, click Repeat.
In the Repetition dialog box, make the changes to the repetition pattern.
Click Save to save your changes.
If you click a repeating item, such as a weekly meeting, Outlook Web App displays a message reminding you that you're editing only a single occurrence and letting you edit the series.
What if I want to know more?