Not necessarily, only that germination rates may be reduced after that time, to a level below which they could not sell them commercially without complaint.

The date is to protect both the buyer and the seller. The date means they have been tested recently to germinate at an acceptable rate (over 60% for peppers) for the year. The customer is guaranteed that they are buying viable seed and they should sprout up nice.. If there are germination issues, it is probably by something the buyer did, not enough heat, buried too deep, whatever.
Even though peppers will be good for a few years when stored properly (cool, dark, and dry) people often don't do as they should so the date is a protection for the seller that a customer can not come back later on complaining of bad seeds since improper storage can great reduce the shelf life of seeds.
Remy

I have a tomato plant that has produced so many tomato it's hard to count them. I have many still on the plant but them are not ripping. I would like to save the seeds for next year but don't no if the seeds from an unripened tomato would produce tomatoes next year.

Gov123,
Saving seeds from anything requires they become completely matured. The amount of time this requires depends on the plant. If you harvest the seed too soon, they will have a reduced viability or can be not viable at all. Think of it as if it were a pregnancy. So tomatoes should be ripe or almost ripe to have good seed with a high germination rate.
Hope that helps,
Remy
PS (this should be read in a helpful tone as I know the computer can make things sound mean when they are not meant to be) since this thread started by PepperGuy was about purchased seed, you really should have started a new thread. If others come along asking about purchased seeds, this all does not fit the conversation and vice versa.