Microsoft has released an update to Outlook for Android that brings a number of improvements to the calendar portion of the app. The update is version 2.2.91 and should be coming to those have the app installed over the course of the next few days.
The biggest changes in this update are the ability to set events on your calendar as free or busy as well as being able to mark events as private when you are sharing your calendar. This is most often used in corporate environments but can also impact personally shared calendars too.
If you are responding to an event in Outlook for Android, you can now add a note to that event so the organizer will see them and you can now respond to an event without notifying the organizer. All of these features are things you have been able to do on the desktop version of the app for sometime but Microsoft is continuing to close the feature parity gap between their desktop and their mobile apps.
If you have Outlook installed on your phone or tablet, expect the update sometime this week. If you want to give Outlook a try, you can download it for free from the Play Store.