You can now use the quick method to create appointments in My CRM calendar of other users. Both you and the user to whom the calendar belongs are added to the User field of the appointment you create.

I have logged into the system as a user called Susan May and I am looking at her calendar. I can now add an appointment for another user.

I need to open the calendar of the user for whom I want to create an appointment:

I've navigated to Brian Little's calendar

I can now click on the calendar and start to enter the details.

I am just adding a 'Sales Review'.

And once it is saved it appears in the target user's calendar.

But if I click to look at this meetings appointment you can see that both the target user and the user who created the appointment are assigned to it.