Outlook calendar 'changes' appointment into a meeting after editing.

AJ, Thanks for suggesting use Windows Calendar App to create Appointments (instead of Outlook Desktop App) with Outlook.com accounts. I tested by creating an Appointment with Windows Calendar and was able to view/edit it using Outlook for Desktop, Outlook for iOS, Outlook for Web, Apple Calendar App, etc.  I will use Windows Calendar App as a workaround until Outlook Desktop App is fixed. 

MG, I'm glad the workaround is working for you. All seems ok so far, I haven't re-installed Office yet as can find nothing anywhere to say that this would work. Windows Calendar seems to play nicely with outlook.com and the phone apps. It's Office Outlook where the problem lies ... I hope your above reply to Barry triggers a response and I'll keep an eye on this thread and nudge again shortly.

AJ, Thanks for suggesting use Windows Calendar App to create Appointments (instead of Outlook Desktop App) with Outlook.com accounts. I tested by creating an Appointment with Windows Calendar and was able to view/edit it using Outlook for Desktop, Outlook for iOS, Outlook for Web, Apple Calendar App, etc.  I will use Windows Calendar App as a workaround until Outlook Desktop App is fixed.

Following is a recap of Calendar issue and workaround to use until it is fixed:  

CALENDAR PROBLEM

Calendar functionality has become a problem for users of Outlook.com accounts.  Appointments created for Outlook.com accounts using Outlook for Desktop become Meetings when viewed using Outlook for iOS, Outlook for Web, and Apple’s iOS Calendar App.  The converted Meetings cannot be edited except when using Outlook for Desktop. The problem may be caused by synching of Outlook for Desktop with user’s Outlook.com account. Until this problem is permanently fixed, a temporary workaround is to stop using Outlook For Desktop to create new Appointments (instead, use Outlook for iOS, Outlook for Web, or native calendar app on your smartphone). For existing Appointments, export your Calendar into an iCal file (and then delete the Calendar from Outlook) and next import the iCal file into Outlook.com using Outlook for Web. See links below for details on how to save and then import a Calendar.

WORKAROUND FOR EXISTING APPOINTMENTS

Step 1 - Save Calendar as an iCal File 

https://support.office.com/en-us/article/Export-an-Outlook-calendar-to-Google-Calendar-662fa3bb-0794-4b18-add8-9968b665f4e6

Step 2 - Delete the Calendar 

https://support.office.com/en-us/article/Delete-a-calendar-9BA1364C-BDB0-41BE-8F66-EAF96698D021

Step 3 - Import the Calendar into Outlook.com 

https://support.office.com/en-us/article/Import-or-subscribe-to-a-calendar-in-Outlook-com-cff1429c-5af6-41ec-a5b4-74f2c278e98c

Barry, I just now noticed that Appointments created using Outlook 2016 appear as Meetings when viewed using Outlook for iOS (but not when viewed using Outlook 2016). Outlook for iOS shows the Meetings with my Outlook.com address as Organizer and as Participant. When viewing an Appointment using Outlook for iOS, the Organizer is displayed as my Outlook.com address (followed by a string of characters that includes the words exchange administrator) and the Participant is displayed as my Outlook.com address (without any additional characters). Please ask the Outlook for iOS Team to fix this glitch. Thanks.

Barry,  AJ's workaround works for me.  I have installed Outlook for iOS on my iPhone and will be exclusively use it's Calendar feature to access my Outlook.com calendar. I have also gone into my iPhone's Settings>Accounts & Passwords and deleted my Outlook.com calendar from my iPhone. Please ask AJ's workaround on the Fixes Page at Outlook website (see link below). Thanks.

FIXES

https://support.office.com/en-gb/article/fixes-or-workarounds-for-recent-issues-on-outlook-com-8c95d913-d96b-4065-9171-e1fa44b03ff5?ui=en-US&rs=en-GB&ad=GB