One reason could be that if the property was listed on more than one multiple listing service, and not listed on each service on the same day, that would explain why a property is showing different days on market. I know for myself, I belong to two multiple listing services---Fairfield County MLS and the Connecticut Statewide CT-MLS. There are times when I get a listing up and running on the CMLS (Fairfield County) and then may take a couple of days to get it on the CT-MLS. I hope that answers your question. Please feel free to contact me for more info. Best Regards, Terri Vreeland, 203-452-3888 ext. 137.