Virto Calendar App supports the overlaying of Exchange personal and shared calendars (Outlook calendars). To overlay Exchange calendars, open the calendar settings by clicking the calendar name.
Scroll down to “Exchange settings” and pick the Exchange calendar you wish to show in your Virto calendar.
Chosen calendars will appear in a single calendar view.
If you are a member of many groups, this view may not be convenient for certain purposes. For example, when you need to view marketing group events separately and need the option to overlay or turn them off, the method presented in Outlook Group Calendar for adding meeting rooms may work better.