Overlay Calenders in Outlook 2007 View The Full Article What is calendar overlay Calendar overlay is a feature in Outlook 2007 that allows you to maximize your view of a calendar while still being able to easily move between multiple calendars. Outlook 2007 How to Overlay Calendars. First youand39ll need to change to the Calendar view, and then select more than one calendar in the list. Now if you hover your mouse over the little arrow icon next to the second calendar youand39ll notice it says View in Overlay Mode. You should click the icon at this point. Now your calendars will be overlayed over top of each other, with the current calendarand39s items visually highlighted. Clicking the icon again would put the calendars side by side again. Switching back and forth between the tabs will visually highlight the items for that calendar. Additionally, you can interact with the grayed items from the other calendars while still in the merged view.