Preheat oven to 350°F. Line 2 baking pans with parchment paper.
Toss challah cubes with extra virgin olive oil (evoo), and toast in 350°F oven for 2 to 3 minutes, or until golden brown. If baking the same day, leave oven on.
Heat 2 teaspoons of evoo in a large ovenproof sauté pan or Dutch oven over medium heat. Sauté celery, onions, and apples in batches, seasoning each batch with salt and pepper. Cook each batch for 5 to 7 minutes, until vegetables have softened.
Return all the sautéed vegetables back to the pan. Toss in toasted challah, dates, sage, chicken broth, and eggs. Mix to thoroughly combine.
Cover and bake in 350°F oven for 1 hour. Uncover, and continue to bake 5 to 10 minutes more, until the top is browned and crispy. Cool slightly before serving.