I just read an interesting W3C Working Draft, Time Ontology in OWL that provides us with insites to the challenges of accurately expressing temporal information. Time Ontology in OWL

“presents an ontology of temporal concepts, OWL-Time (formerly DAML-Time), for describing the temporal content of Web pages and the temporal properties of Web services. The ontology provides a vocabulary for expressing facts about topological relations among instants and intervals, together with information about durations, and about datetime information…A use case for meeting scheduling is also shown. In the appendix we also describe a time zone resource in OWL we developed for not only the US but also the entire world, including the time zone ontology, the US time zone instances, and the world time zone instances. “

For those who have the time to read about time, I want to you to be forewarned that this document is not an easy read. Time is a complex issue that takes time to understand. The reader may have to take the time to read certain portions multiple times since the text is laced with statements such as this:

“Intervals are, intuitively, things with extent and instants are, intuitively, point-like in that they have no interior points. It is generally safe to think of an instant as an interval with zero length, where the beginning and end are the same.”

Relative to time zones and daylight saving time, I have now learned that:

“If we were to conflate time zones (i.e., geographical regions) and time standards, it would likely result in problems in several situations. For example, the Eastern Standard zone and the Eastern Daylight zone are not identical, since most of Indiana was on Eastern Standard time all year. The state of Arizona and the Navajo Indian Reservation, two overlapping geopolitical regions, have different time standards during the daylight saving times — one is Pacific and the other is Mountain.

Time standards that seem equivalent, like Eastern Standard and Central Daylight, should be thought of as separate entities. Whereas they function the same in the time ontology, they do not function the same in the ontology that articulates time and geography. For example, it would be false to say those parts of Indiana shifted in April from Eastern Standard to Central Daylight time.”

All this makes me wonder if I have appeared to be a simpleton to my colleagues in India when I write from my geographical location in Phoenix, Arizona that I would like to propose that we have a conference call at 6:00 am PDT / 6:30 pm IST. This must seem even more confusing, when I consider that starting on October 30, 2006, in order to schedule the call for the same time period I shall have to write “6:00 am MST / 6:30 pm IST.”

I do think that is incorrect to write “6:00 am PDT” since Arizona is not in the geographic Pacific Time zone. I really should write “6:00 am MST” all year long, but I worry that it would be misread by others in the US as “MDT.” then the scheduling would get confused and someone might miss the call.

I never worried about this before, but now that the W3C has me thinking about such things, I am quite concerned.

Bill

1. Thanks a lot for the informative comment. I will correct the post to say Daylight Saving Time.

2. The Dine Nation factoid is very interesting. Hope someone from Microsoft is reading it.

Even when we think that we have made a definitive pronouncement on the topic, if we drill down, there is always just one more exception or piece of trivia to be found.

I have two observations to add to this timely topic:

1. There is, although not many know it, some confussion over terminology. Most people probably refer to the summer time time shift as Daylight Savings Time. That is officially incorrect. The proper term is Daylight Saving (no “s”) Time. “Saving” is an adjective that modifies “daylight.” Nevertheless, popular usage has a way of imposing itself. Using Google as a linguistic meter, one gets 9,760,000 hits on “daylight saving time” and 6,580,000 on “daylight savings time.” The later is also now referenced in some dictionaries.

2. One of the states that everyone thinks does not go on to Daylight Saving Time (DST) is Arizona. Just take a look at your time zone setting in the Microsoft Windows clock. No DST change according to it. I am an Arizonan, and I have made the propagation of the news that this is not true my cause celebre since most Arizonans are living under that misconception. The truth is that most of Arizona does not go on DST, but the northcentral and northeastern portion of the state, which is made up of the Navajo Native American Indian reservation, or the Dine Nation as they prefer to call it, does go on DST. While most of the Dine Nation is in Arizona, portions flow over into Utah and New Mexico. These portions of the Dine Nation shift to DST, so the whole tribal area does. It is the largest and most populous reservation in the USA, so I guess it is big enough to get away with it. I have frequently asked if this is just a subtle way of making a statement. I am glad they get away with it.

Now it’s time to go.

Bill Howard