It was never all that realistic to ask us to get up from behind our computers anyway, so at least there's an app that realises this. F.Lux software will change the light on your computer depending on the time of day, imitating natural daylight patterns.
Computer screens have a slightly blue tint, and while this is fine during the day, it can cause problems for those of us who keep tapping away into the night. What happens is this disrupts our production of melatonin, the hormone that regulates the sleep cycle, as the light-sensitive pineal gland near the centre of the brain responds to blue light by suppressing melatonin. This keeps us from getting a good night's sleep, or can even cause insomnia.
Enter F.Lux - the free software which will automatically adjust the light as they day wears on. Free to download here, the app will ask you where you live so it can calculate sunrise and sunset; alternatively you can enter a different time zone, handy if you're trying to adjust ahead of a long-haul flight.
The app will also enquire about the light in your room, be it tungsten, halogen, fluorescent or daylight. Based on the information, it adjusts the colour temperature of your screen to mimic the lighting in the room. So there you have it - your computer can now adjust to what goes on outside your window so you don't have to.