1. Click File > Save Calendar to create a backup. You can re-import the calendar if something happens. There won't be any way to write protect your own calendar from yourself due to the mailbox folder permission structure. It could theoretically be possible using powershell as an exchange admin.

2. You could create a shared mailbox or 2nd mailbox/account that contains calendars and then give your main account read-only access to them. This can be done easily in enterprise but I don't know if that kind of sharing is possible between consumer live.com/outlook.com accounts.

I hope these ideas help :D

It could theoretically be possible using powershell as an exchange admin using Get or Set-mailboxfolderpermissions -identity %primaryemailalias%:\%folder% but that is a terrible idea in enterprise to be honest.

1. Click File > Save Calendar to create a backup. You can re-import the calendar if something happens. There won't be any way to write protect your own calendar from yourself due to the mailbox folder permission structure.

2. You could create a shared mailbox or 2nd mailbox/account that contains calendars and then give your main account read-only access to them. This can be done easily in enterprise but I don't know if that kind of sharing is possible between consumer live.com/outlook.com accounts.

I hope these ideas help :D