The OPTIMAL Calendar lets you use two different kinds of notes: Event Notes and Calendar Notes.
When you create an Event on the Calendar you may place a short bit of descriptive text (a 'note') in the Event Text field. This note will appear whenever you view this Calendar Event. (If this event is a repeating event, the note will show up in all instances of the event in the Calendar.) This note is called an Event Note, and it is linked to the Calendar Event you created.
You may also attach notes to a specific day in the Calendar, without creating an Event. This note is called a Calendar Note. A Calendar Note is not attached or linked to a Calendar Event.
To leave a Calendar Note on a specific day, find that day on the Calendar and click on the date. You can then leave a note that is just for that day. It's not tied to any Events for that day- it's separate and will remain in your Calendar even if you delete any Events that occur on that day.
For example, lets say you create a Calendar Event that repeats every two weeks on Monday and the Event Note you enter says "Pizza with Uncle John". Each link in the Calendar will have this "Pizza with Uncle John" note associated with it, and you'll see this note if you hover your mouse over the Event links (or click on the Event links).
What if one Monday Uncle John is busy and can't make it to have pizza? You can go to that specific date in the Calendar and click on the date link (not the Event link) and enter a Calendar Note for that day that says "Uncle John couldn't come for pizza tonight".
Because this is a Calendar Note, it will only appear on the day you left it and won't not appear in any of the other Event links for the "Pizza with Uncle John" event that you originally created.
When you view an Event and there is a Calendar Note attached to that particular day, you'll also see a link to it just to let you know that there is a Calendar Note for that day as well.
This flexibility lets you to set a "main" Event note for an event but also allows you to leave notes specific to a particular day when that event occurs. You don't have to create an Event to leave a note on any particular day in the Calendar- you can just go to that day in the Calendar, click on the date link and leave a Calendar Note.
When you view the Calendar and there are Calendar Notes for a particular day, a small Note icon appears next to the date in the Calendar:
Clicking on the Notes icon will display all of the notes for that day in the Calendar.