There are a couple ways to handle the type of event. One possibility is to use another property, such as "event type", and then limit the possible choices, much as we limit what you can enter for the type of a unique item. Another way is to use categories. All of your realm law pages could be tagged like this:
[[Category:Far East]]
[[Category:Cathay]]
[[Category:Laws]]
[[occurrence date:: August 5, 2014]]
Then when you build your timeline of realm laws, you only include events that are tagged with Cathay and Laws. Or, if you want to build a timeline for all events in Cathay, just do a time of everything in the Cathay category. Or do Laws and Far East for all laws passed on the Far East.
One of the benefits of using categories is that it is easier to to find a set of pages using a category than by using a property. The wiki has built-in tools for categories, but we have to use our own tools for properties.
You can refer to the unique items time lines for an idea of how this is done. There are also other semantic templates that include semantic queries using properties and categories.
