Currently Reclaim only has full support for Google Calendar. But if you have a Google calendar as well, you can import Office 365, Apple iCloud, and other external calendars into Google and then use the Calendar Sync or Connected Calendar features ensure that Reclaim is aware of your events on those other calendars and schedules Habits, Tasks, and Smart 1:1s around them.
Note: There are some known issues around significant delays between iCloud / O365 calendars and Google Calendar. It can take hours or days in some cases for changes between Google Calendar and O365 / iCloud calendars to fully synchronize. Reclaim unfortunately has no control over these issues.
To connect a non-Google calendar
Make sure the calendar you want to connect is shared with your Google account that you are using to for Reclaim. Here are resources to sync common calendars to your Google Calendar:
Once you've connected your non-Google Calendar, you can make Reclaim aware of it in two different ways:
You can have the source events copied to the primary calendar of your main account in Reclaim using Calendar Sync with your shared calendar.
You can simply make Reclaim aware of this new imported calendar by identifying it as a Connected Calendar.