The house we just bought has a furnace from 99 but the AC outside is from 92. That's not uncommon, as people frequently only replace them when either they stop working (and it's rarely at the same time) or sometimes to improve the value for resale. If it was part of your contract that they were to be new, then you should talk to someone about it. Home inspections before a purchase are always advisable as a lot of major issues can not be detected by the average person.
An EASY way to find out how new your Furnance and AC unit are is to look for the metal "tag" that they pretty much all have that has the date of manufacture on them. Furnaces, water heaters, etc. usually have this. If your AC was to be replaced before the sale, you should contact your lawyer and/or realtor. On the other hand, if the seller said it had "newer HVAC" and you didn't find out exactly what "newer" meant until after you bought the home you may not have any grounds for any action. Either way, I'd check with your attorney if you have concerns.