I have had seeds sprout just fine that were four or five years old. It varies by variety, some seeds keep their vitality better than others. And germination rate does tend to go down over the years, so with older seed, sometimes maybe 50% of them will sprout instead of 90-100%%. So plant them thicker. But the only way to tell if they are still viable is to plant them.
Well, not the only way... you can take some of your seed and put it between damp paper towels and put it in a ziplock baggie and see if it sprouts. If it doesn't sprout that way, it probably won't in your garden either.
But otherwise, what have you got to lose? Plant them and see what happens. If you want to start seeds indoors in winter to have plants ready for spring (as I do every year), maybe just start them a couple weeks earlier than you would otherwise. Then if for some reason they don't sprout you still have time to start over with new seeds.