I was going thru listings that expired 12/31, and when looking thru new listings for 1/01/07. I noticed one expired where the listing agent put it in as a new listing today and now states DOM= 1

Are agents allowed to do this? Doesnt it need to be Expired/Relisted.
I am trying to find info in the MLS pertaining to guidlines and doing this. I have found other listings that expired yesterday, but have been extended.

Depends on your MLS. Of the two I belong to one will allow you to extend it anytime with in 30 days at no penalty; the other, once it goes expired, charges a "reactivation fee" to extend it but would not charge extra for putting in a "new" listing for the same property with the same agent. The listing agent may also be trying to get attention by having it show as new (not all agents read the expireds). The DOM will calculate from the listing date automatically. Again depending on the MLS it may or may not include prior market time either with the same agent or even a different one. Where it does include prior marketing time it may need to be expired a certain number of days before it resets to the most recent listing date for calculating DOM.

Where I have seen it include prior time the tracking is off the tax map number field. I relisted an expired from another company several years ago when I was with a different broker and it showed their marketing time cumlative with mine but a minor change (extra - or . or 0, I don't remember which) to the tax map number by our clerical staff dropped the prior listing market time.

This is known as re-listing. Some MLS systems actually allow agents to do this any time during a listing. It really throws off the numbers. I wrote an article about it that you can read here:

http://www.soldbyrobert.com/content/view/40/2/

R