If your calendar on Microsoft Outlook has become a disorganized mess, you might want to reset it and start again with a clean sheet. This can be quicker than trying to remove or edit individual events and appointments, particularly if your calendar covers several years. Although Microsoft Outlook doesn't include a specific reset function, the program does allow you to reset and restore the calendar by deleting all items.
Launch Microsoft Outlook.
Click "Calendar" under "My Calendars" in the left-hand navigation pane.
Click the "View" tab in the main program menu.
Click "Change View" in the "Current View" group.
Click "List." This displays a list of all your calendar items in the main program pane.
Click anywhere in the item list. Press the "Ctrl" and "A" button on your computer keyboard. This selects all items in the calendar list.
Press the "Delete" button on your computer keyboard. This resets the calendar by deleting all items.
Restoring your calendar by deleting all items includes deletion of the holidays that Outlook automatically adds to the calendar. You can add holidays to the restored calendar by clicking “File,” followed by “Info” and clicking the “Add Holidays” button under “Calendar Options.”