It would be very helpful to be able to add a calendar entry without having it obligatory linked to a program. For example, I'd wish to enter the national holidays in the calendar but I can't because it needs to be linked to a parent program.
I like this as a starting point - but I think the ability to add entries outside of a program would be very useful. For example, if a colleague asks for an email in a month's time, you don't want to have to create a program and a dummy send date just as a placeholder. Ideally, you could simply add a new calendar item "schedule" which you could use to avoid any potential scheduling issues, and as a placeholder until the email is built.