What I love about living in the tropics, is that the time of sunrise varies very little. In my location in South India, sunrise is between 5:45 AM and 6:30 AM and sunset similarly between 5:45 PM and 6:30 PM. Twilight is short. So essentially, I don't need an alarm to wake up. Sunlight streams through my windows in the moringing, and when it's dark I know that its time to stop working. I love that. I used to live Seattle earlier, and never got used to the wide variations in when sunrise and sunset actually happened.