I have always felt like my natural sleep/awake cycle is longer than 24 hours (maybe 26 hours). If a majority of participants said they felt like only 30 days passed, then their cycles are 32 hours long.
I wish we can one day evolve into a society where time doesn't have to be so stringent.
I had this problem for most of my life, except for when I had no job and was doing Ironman training full time. Then I think my sleep/awake cycle was more like 6/6. Sleeping well was the best part of all that. I read somewhere that our cold weather ancestors evolved to expend about 6000 calories per day.
The"spontaneous work" theorized by Che Guevara can lead us to a time-cycle free way of life. Im pretty sure life was organized in a communist or socialist way in this cave : no boss, no social classe, and the belief than everyone in the cave walk toward a common good by achieving voluntary usefull job.