I've always understood intellectually that humans, like most critters on Earth, have an innate internal clock, and as someone who's worked rotating shifts of various kinds for over a decade now, I've had a lot of experience at tweaking and recalibrating mine. But it still surprises me how utterly, utterly surreal it feels when that mechanism gets truly and seriously messed with.
Now, I've been working nights the last month or so. This was to large extent my own choice, and I liked it just fine, but it is unusual for me to stay on any shift long enough that it starts to feel completely normal. But by last weekend -- two consecutive 8PM-8AM shifts -- I was so solidly adjusted to a nighttime schedule that the little clock in my brain was absolutely and completely certain that night was day, to the point where I kept thinking of it as day and half-expecting day-shift stuff to be happening. The fact that it was dark seemed irrelevant. Or rather, it seemed perfectly sensible: it's dark during the day, of course. It always is.
OK, that was weird enough. But then I got to the point where I had to think about switching back over to day shifts, which I'm starting on Monday. (Normally, I'd have another full week to make the transition, but I have to cover for someone who's going on vacation.) In the past, when I've needed to get myself off of night shift, I've usually done it by trying to shift backwards: waking myself up earlier so I'd be tired earlier. This is hard to do, though, most especially if you've been on nights long enough that your internal clock genuinely believes that bedtime isn't supposed to come before 8AM. Plus, it involves not getting enough sleep, for however many days it takes to accomplish the transition. The radical alternative is to do it the other way: to attempt to stay awake for something like 30 hours. This is faster, but it sucks, and attempting it often results in dropping of exhaustion around 2 PM and waking up in the middle of the night, which isn't quite the desired effect.
I was contemplating doing the latter, anyway, when it occurred to me: there's absolutely no reason I'd need to shift forward all at once. Having crammed in three days worth of work on the weekend, I only had 16 more hours I needed to put in somewhere, with it not really mattering when I showed up... which gave me a full week of flexible hours before I had to be ready for the day shift.
So, I've been rotating forward slowly. On Monday I went to sleep at 10 AM and woke up at 6 PM; Tuesday it was noon to 8, Wednesday 2-10, and today I fell asleep at 4 PM and woke up at midnight. At this rate, come Monday, I'll have wrapped myself around so I'm sleeping 10PM-6AM, which should be absolutely perfect.
I'm not sure if I recommend this method or not, though, because it's... did I use the word "surreal?" Being awake during the day after living nocturnally for so long is bizarre enough: I remember walking down the street at mid-morning on Wednesday feeling kind of freaked out by the fact that it was so bright and there were so many people and wondering at the fact that other humans could possibly consider this normal. I can't help but wonder if people who've just been released from prison -- or at least from dungeons -- feel the same way.
Anyway, that was weird enough, and having afternoons come at the end of my day is also weird enough, but the truly surreal thing is how my internal clock just seems to have given up and broken. I have no sense of time whatsoever now. I hadn't realized before just how much we define our days as divided by our sleep periods. Or rather, I had -- every shiftworker, I think, has the innate sense that it's not tomorrow until you've slept, no matter what the clock or the morning person who's relieving you think -- but I hadn't realized just how deeply that's embedded into our subconsciouses. I guess it's true that you don't ever properly appreciate things until you have to do without them. Because I find that I honestly can't remember whether something happened today or yesterday, for any definitions of "today" and "yesterday" at all. There's no sense of "before I slept last" being a different period than "after I slept last," and, man, that doesn't sound terribly disturbing when I write it out like that, but, believe me, it's disconcerting. Everything runs together into a big, undefined temporal blur. And I have to keep looking at clocks and calendars to figure out things I really ought to know intuitively, like how long I've been awake and what day of the week it is and whether it's morning or night.
It's a fascinating personal experiment, really, which is why I've rambled about it at such length (and probably bored the crap out of anybody who isn't me). If nothing else, it's given me a greater appreciation of how much that internal clock normally does for us, not to mention a more visceral understanding of the cyclical nature of time. It's also proving quite successful... Staying awake an extra couple of hours each day is easy enough -- much easier than trying to go to bed earlier -- and I'm getting plenty of sleep and remaining a productive human being, even if I'm being productive at odd hours. But I really don't think I'm going to make a regular habit out of this.
Now, if you'll excuse me, it's almost 2 AM. I think I should probably be getting ready for work.