Hotmail calendar on mac is read only - how change?

Hello gurglingmilk,

Let's try to resolve the issue by completing the steps listed here: Add, modify, or delete events in Calendar on Mac - Apple Support that are also listed below.

"Modify an event

1. In the Calendar app  on your Mac, double-click or force click the event to open it.
2. If you created the event, you can do any of the following:

• Create or modify all-day or multiday events
• Set up a repeating event
• Add location and travel time to events
• Set alerts for an event
• Invite people to events
• Add a FaceTime video call
• Add notes, a URL, or files to events
• Move events to another calendar
• Use different time zones

Siri: Say something like: “Change my lunch from 12:30 to 1 p.m.” Learn how to use Siri.

To change an event’s start or end time, you can drag the top or bottom edge of the event. You can also drag the left or right edge of all-day events.

To change an event’s date or time, drag the event to another day or time. You can also drag the event to the small calendar in the bottom left of the calendar list. To view the calendar list, choose View > Show Calendar List.

If you didn’t create the event, you can change your acceptance status. You may also be able to leave a comment for the event organizer or propose a new time. See Reply to invitations."

Best regards.