Many marketing websites DO show "DOM" days on market, however only a Realtor will be able to give you a definitive answer my looking in the MLS to see what the current DOM is,,
& even then, the property could have been on the market previously,,the MLS is even a little sneaky with that showing a DOM & a CDOM "cumulative days on market", so the total may actually be higher.
If you have a particular property in mind, I can check this for you & give you the history if it was on the market previously. You can also sign up to search MLS listings with a Listingbook acct., this program allows you to search the MLS just like I do & it DOES display DOM.
Email me directly as I won't check back on this same Trulia posting.