Complex sentence: They built City Year with the conviction that one person can make a difference and since its inception, City Year has promoted the vision of service as a common expectation--and a real opportunity--for citizens all around the world.
Split into simpler sentences: They built City Year with the conviction that one person can make a difference. Since its inception, City Year has promoted the vision of service as a common expectation--and a real opportunity--for citizens all around the world.