DOM for me is categorized for my sellers & buyers as follows: 

Active DOM: wishful thinking.

Pending DOM: in contract-what the market is presently doing.

Sold 90-180 days DOM: Historical Data, what the market recently did.

Expired/Canceled/Withdrawn DOM: Failed To Sell

For a CMA -- they are categorized.  

It depends upon what I'm doing.  A market report gets sold DOM data, a CMA gets the entire picture. But on my market report it's reported as DOM average and median for solds for that month.

I do, because if a property was listed and didn't sell during a specific time period, it did indeed have a bunch of extra days on the market.  And it's good when you can shed light on the reason why it lingered.

We use the figures provided by the MLS.

Yes I look at the entire picture.

The calculations should be used for buyers and sellers; then one should also do a visual to see if anything is wrong with the property to warrant having expired or excessive days on the market.

For current listings and sales no. For an individual home that was listed once or twice before, i make a note of it

I use what mls shows.

I do not because there are too many variable for reason why certain properties were taken off market . Our MLS also calculates DOM in a report called "area market reports". When I use this I have the ability to map out an area so I get in essence a sub market area that is more specific to my subject property.

Solds only.

Yes, I do reveal the stats that matter to the owner are SOLDS.

Now I am prepared to share the consequence of the mistakes others make and how pricing 10% too high, to create negotiating room and piling on, can result in a a long-term relationship that was not intended.

Agents, I remind then, do not set the price, owners do.

Our mls calculates the dom . 

Our MLS doesn't and it paints an incorrect reality !

I don't generally use cancelled or expired listings. They have been rejected by the market for some reason or another. 

Interesting question, but I think not.  If I'm talking about 'solds', the failed listings don't play into that conversation. Likewise with the 'actives'.  However, in a market analysis, the days on market of the 'failed' listings along with price reduction data might be more important.

Just my personal bias.

I leave that up to the folks at the MLS

In our MLS you can take it off for 90 days and it zeros out. 

We do not see many expired or canceled listings, so do use the DOM of those listings that sold (or active/UC).

The most important DOM when I'm on a listing appointment is the average and median for sold listings and ones under contract.  Expireds and withdrawns haven't been chosen.  And since, in my mind, we're ultimately trying to get at how long it takes to get chosen, I leave them out.