I am not sure of your customers needs, but sometimes making the quick and dirty banner just looks better than trying to have a changeable date field...
,,, I work for a school district. We have a lot of banners that change every year - banners that announce things like the start of enrollment. The direction our customers have chosen to go is withe the least expensive, un-hemmed banner that will stay up for a month or so.... we had designed the original to take vinyl stickers, but it looks a whole lot cleaner to just print a new banner with the new dates.