I don't know anything about why it happens, but you're definitely not alone. A friend of mine has it pretty bad; trying to adhere to a nominal 24hr has utterly

I don't know anything about why it happens, but you're definitely not alone. A friend of mine has it pretty bad; trying to adhere to a nominal 24hr has utterly failed him. If I recall, his body runs on about a 26hr schedule in a 13 day cycle. He fought it for a long time but ended up just being a zombie all day long until he found work that let him roll with it (which means for some portion of the cycle he's working midnight to 8am) It's super inconvenient; if anyone knows of any potential resources I would happily pass them along to him. He's found something that works, but it's pretty inconvenient for... you know... integrating with the rest of the world.