In order to find out about the true DOM, you will have to talk to a Realtor. This is not just trying to get business for Realtors but its because Realtors have the resource to find out. The majority of the Realtors will help you find information for free anyway.
Most of the MLS keep history on a property. So your Realtor will be able to look through all the listings and let you know the status and DOM on a house.
I usually let my clients know about the history on a house, where it been on and off, had contracts on and fell out, had price reduction and for how long, whether it had been with several Realtors so the dates were reset, whether it has been off the market due to holiday or family illness, whether there were upgrades to the house since it came on the market, whether the house came on the market in the deal of winter (slow season) etc. I may have to talk to the listing agent to get some of the story.
The reason I say all these is because you can't really judge how a house is by only looking at DOM, a number. There is a lot of misconception and misuse of the MLS information. Without property clarificacion, the consumer will not be able to get a clear picture of the house and it's status. Ask a professional to put things in perspective helps.
Your best bet is to talk to a local Realtor that knows the are in question. They will usually know inside information of seller contributions and concessions as well as the history of a particular property on the market.