The KnownProperty property may access a property of the event giving its identifier. For instance, the KnownProperty(exEventRepetitive) property indicates whether the current event is repetitive or not. The property returns True, if the Repetitive property is not empty and valid. 

The EventKnowPropertyEnum defines the %identifiers that can be used in formula <%=FORMULA%>, in any of the following label properties

• DefaultEventLongLabel, defines the HTML labels for events, when it fit entirely in the event's body.
• DefaultEventShortLabel, defines the labels for events ( no HTML attribute is applied ), when it does not fit the event's body
• CreateEventLabel, defines the label when creating a new event by dragging
• UpdateEventsLabel, defines the label of the events being moved or resized at runtime
• Event.ShortLabel, defines the event's short label, or the label to be shown when the LongLabel does not fit entirely the event's body. The ShortLabel displays no HTML tags
• Event.LongLabel, defines the event's HTML long label, when it fits the body. If the LongLabel does not fit entirely the event's body, the ShortLabel is displayed instead.
• Event.ExtraLabel, defines the event's extra HTML label. The event's ExtraLabel is displayed ONLY, if the LongLabel fits the event's body

The label properties supports the following identifiers. These identifiers can be used in FORMULA expression:

• %1, Indicates the starting date/time of the event as DATE type, equivalent with Start property
• %2, Indicates the ending date/time of the event as DATE type, equivalent with End property
• %3, Indicates if the current event is an all day event as BOOL type, equivalent with AllDayEvent property
• %4, Indicates the identifier of the event's group, as LONG type, equivalent with GroupID property.
• %5, Indicates the caption of the event, as STRING expression, equivalent with Caption property.
• %6, Indicates the extra data associated with the event, as VARIANT type, equivalent with UserData property.
• %7, Gets or sets the duration of the event as FLOAT expression. Above you can find how you can display the duration of the event in hours, minutes... 
• %8, Specifies the repetitive expression of the event, equivalent with Repetitive property.
• %256, Gets the margins of the event in a short format, as a STRING expression. The ShortDateFormat property defines the short date format. The ShortTimeFormat property defines the short time format.
• %257, Gets the margins of the event in a long format, as a STRING expression. The LongDateFormat property defines the long date format. The LongTimeFormat property defines the long time format. 
• %258, Gets the starting date ( not including the time ) of the current event, as a DATE type.
• %259, Gets the starting time ( not including the date ) of the current event, as DATE type from 0 to 1.
• %260, Gets the ending date ( not including the time ) of the current event, as a DATE type.
• %261, Gets the ending time ( not including the date ) of the current event, as DATE type from 0 to 1.
• %262, Gets the label of the owner group, as STRING expression, equivalent with Caption property of the Group's event.
• %263, Gets the title of the owner group, as STRING expression, equivalent with Title property of the Group's event.
• %264, Indicates if the current event is a repetitive event, as BOOL type. This flag returns TRUE, if the Repetitive property is not empty, and the expression is valid.

For instance, the LongLabel = "Start: <%=%1%><br>End: <%=%2%>", displays the starting margin of the event on the first line, while on the second line it displays the ending point of the event.