Tyres expire about six years after the date it was manufactured. This mean that after six years the components of the rubber that was used in making the tyre has changed, it is no longer going to be strong as it was meant to be, it will no longer hold a pressure it was meant to hold, it won't have the grip on the road it was meant to have; but it doesn't automatically mean that the tyre will explode, or cause accident when used, but it simply means that it is time for you to change it before a disaster happens

Thanks so much for this information @ityfrank. Though I don't have car for now, but who knows what will happen tomorrow. No knowledge is waisted. I strongly believe with you that old tires can lead to road accident. After 5 years, the tires of our car or whatsoever is good to go.