Pumpkins should be harvested when they are ripe, usually around the end of summer or the beginning of fall. A pumpkin is ripe when it is orange all the way around, has a hard stem and skin and sounds hollow when slapped or thumped.
Some pumpkins are still completely green when they are ripe. If color cannot determine ripeness, the other two methods should be used. Once harvested, the pumpkin's color stops developing. Wear gloves when harvesting a pumpkin, and use a sharp knife. Leave several inches of stem attached to slow down rotting. Expose the pumpkin to the sun for 10 days to cure it.