and not let the sun rise, how long would it take before Equestria froze and all the food ran out?

3322152 Depends of how much food is storage. And I think a good majority of the population would have starve to death in less than one year most likely in a few months at the most and eventually those who storage food will run out of food and eventually die out

3322152 They would just switch to zap apples.

As for warmth, they do have clothes to keep themselves warm.