08/04/2002-09/04/2002 @04:15:27 ^04:41:39

Threshold Points: When Does A New Day Begin, Anyway?

See that date above? See how there's two of them? In today's second update, let me tell you a story...

Long ago, there was a time when I'd actually be asleep before midnight. But as I got older, it began to be the case where I'd be still up after the clock had struck twelve. Nothing brought this change into sharper relief than in 1996, when my mum and I moved out of my dad's house. No longer living with a man both accustomed to early rising and retiring, and such a light sleeper that you couldn't do anything that wouldn't wake him up, my day quickly shifted several hours forward.

This came with difficulties, not least getting up for school in the mornings. But a major one was what to do about my diary and so forth. If I did something after midnight, did that count as today, or tommorrow? Well, it was always counted as "today", as I wrote my diary last thing at night before going to bed. But there were other troubles too, for example, I wrote a program that made my Risc PC log when it was switched on or off, and it put blank lines between days. But when could we be sure a new day started?

The solution hit me later. Redefine midnight. More specifically, invent a new "start of day" concept, called the Threshold Point. This was the time that I'd most likely be asleep, so it would be a new day when I woke up. In 1996, in fact on 3/11/1996, this was chosen to be 05:00.00. This has held up, most of the time; out of five and a half years of life, it can't have been much more than two dozen occasions since have I been awake at 5am.

Therefore, by my reckoning, right now, at half three, it's actually still the eighth. But when you're thinking more accurately than to the nearest day, it looks weird: you'd have 8/4/2002 02:00.00 actually after 8/4/2002 22:00.00, for example.

Hence the small modification to update-blog - if it's after midnight but before the threshold point when an entry is added, it inserts two dates into the title, because depending on how you look at it, it could be today, or it could be tomorrow, at the same time.

You get me??