A common comparison used a million seconds is 11 days and a billion seconds is 31 years. I find a comparison of people is easier for people visualize than lengths of time.
For westerners: 1 million people is considerably more than the population of Seattle or San Francisco, but far fewer than in Adelaide. Not small cities, but nothing like NY, LA, Sydney or Melbourne. 1 billion people is everyone in North America AND 80% of everyone in Europe.