How many days are most people going to survive when the sun explodes?

If the sun were to suddenly explode, often referred to as a supernova, the immediate effects would be catastrophic. However, the sun is not expected to explode in this way; rather, it will eventually expand into a red giant and then shed its outer layers over millions of years. If the sun were to somehow disappear suddenly, Earth would likely remain habitable for a short period of time, possibly days to weeks, before temperatures plummeted and the planet became inhospitable. Most life would not survive long without the sun's heat and light.