[scott_w]

I read the first chapter and found that his evidence was based on conversations with other programmers. In this day and age, there's enough information for the author to collect more empirical evidence in the form of commits to open source projects.

One could take a sample of GitHub projects and commit times. You would have to find out the contributors' time zones, and adjust accordingly.

You need to balance the hobby contributors against corporate contributors i.e. those being paid to contribute.

If you wanted to make things really interesting, you could try and gauge code quality based on time. Perhaps trying to assign bugs against the commit they appeared in.

[CWIZO]

Swizec has done just that. You can help him out by giving him access to your GH commit history here: http://nightowls.swizec.com/

Don't know why he hasn't mentioned this, maybe he just hasn't come around to writing about it yet.

disclaimer: I'm one of the guys he interviewed.

[gbraad]

Commit times do not necessarily convey the correct information; in the worst case i could have worked two days on a commit, or even commit it the following day. Time zones are also not accurate when travelling is involved for a developer/engineer or eg. Is it even correctly set. I believe evidence comes from first hand, conversation or questionaire

[forensic]

The social science approach would be to use both. Detailed case studies are essential and should be the starting point. But hypotheses extrapolated from those case studies could then be examined with statistical analysis like this.