Kirk has a long circadian cycle

[damaskrose32.livejournal.com]

I'm pretty sure this is a mention in a long fic, but Jim has a longer than average sleep-wake cycle, which McCoy ends up explaining to a puzzled Spock after Jim works multiple shifts on the ship over a period of time. It's definitely pre-Into Darkness, so it's easily 5 or more years old, but I can't remember what it's called or find the right keywords to find it.