All questions regarding mapmaking for Heroes of Might and Magic 3: The Shadow of Death.

In SoD, it's not possible. Unless in WoG. There is a workaround, but it's quite indirect: a message in an event within the city. You'll see it the day after capturing the city. But it needs to repeat every day and will be displayed again and again after each capture. If the city capture must happen on a specific day, no earlier and no later, then it's simple: place an event in the city for the next day.