One of the big pluses of our migration to Office 365 is moving our small company Intranet, currently on an internally hosted SharePoint 2010 Server, to SharePoint in the Office 365 environment.
I had setup a few departmental team sites in 2010 that were never used. However, one department did end up using the Shared Calendar feature in 2010 and put a number of meetings and reminders in it - including recurrent appointments.
I setup a new Group in 365 for them and attempted to connect my personal Outlook to both Calendars - the one in 2010 and the one in the 365 Group. While I was able to connect to both via Outlook, my thoughts of easily copying appointments from one calendar to another were dashed when I realized that my group calendar in Outlook was not updating the copied appointments to the hosted version in 365. If I created a test appointment in Outlook, no problem - it showed up on the web very quickly. But the copied appointments would not - especially repeat ones.
SharePoint 2010 allows me to export to a Spreadsheet link - which I can then save as a standalone spreadsheet file. Additionally, SharePoint 2010 allows me to export to a stand alone Access file. Other export types aren't as clear.
The problem is - 365 Groups Calendars only seem to import an ics file.
Any suggestions on the best way to transfer this calendar from 2010 to 365 Groups?
Bear in mind that Office 365 Group calendar is an Exchange Online calendar and a SPO Calendar is just a list...so this seems to be the main reason why you are not able to copy items between both calendars.