property Event.Underline as Boolean
Retrieves or sets a value that indicates whether the event appears as underlined.

TypeDescription
Boolean A boolean expression that indicates whether the event appears as underlined. 

The Underline property is used to specify the font attribute of the event's date. Use the Events property to access the Events collection.

The following VB sample shows how to apply Underline font attribute to "today" date:

Calendar1.Events.Add(Date).Underline = True