My customers asked about resource calendars and where do I increase the advanced booking settings in Office 365. This is done via powershell. You have to set-calendarprocessing “resource” –bookingWindowInDays 365.

 

In my case I only had one change to make so I could do the following:

 

Get mailbox –identity room1 | set-calendarprocessing –bookingWindowsInDays 365

 

You could change all resources by using the following:

 

get-mailbox | Where {$_.RecipientTypeDetails –eq “RoomMailbox”} | set-CalendarProcessing –BookingWindowInDays 365.

 

BTW – default setting is 180 days.