What is the best time to transplant daffodils?

Normally you leave daffodils in the ground from year to year. If the clump is getting too big, and there are not as many blooms as expected, then the clump will need to be split. You can do this when the plant is flowering, but you shouldn't expect them to bloom the next year. For blooms it is best to wait until the flowers are gone and the leaves are beginning to turn yellow. At that point the leaves have sent all the energy to the bulb that they are going to, you can separate the bulbs and replant.