To merge several calendar data into one calendar, switch the Calendar to the list view and:
- drag the items to the destination folder,
- or use the Move to folder command.
To do that, perform the following steps:
- Select the calendar you want to remove and switch to the list view.
- In Outlook 2010/2013, navigate to View > Change View > List
- In Outlook 2007, navigate to View > Current View > All Appointments or By Category
Note: Contacts folders can be merged the same way; the only difference is that you will need to use the Phone list view.