It's a bit of a cliché to say ghosts only come out at night, a very old one but there's no proof of any preference. Plenty are seen during the day.
Seven years living with that going on....and only now do you get the publicity !
I can see why they have decided to market the house as haunted. If they sell it pretending it is not haunted, and the new owner notices that, they may be forced to cancel the sale.
If they make it well known it is haunted, they can use that in the marketing instead.