Even in developed countries like the U.S. (where many but certainly not all of us Dopers live), we still say “tomorrow” when it’s 12:30 a.m. or 3 a.m. or even 4 to 4:30 a.m. and we’re technically speaking of “today” (since it’s past midnight) but we’re referring to the day that’ll start for most people around dawn or the hours after the dawning of the sun, when schools and businesses do most of their activities and most people live their daily lives.
In ancient Israel the official start of the day was at dawn, which is how days were marked. Same is probably true for pretty much all ancient societies, unless I’m mistaken. Heck, I remember learning about a Native American tribe that considered the dawn of each day to be the creation of a brand new universe/cosmos (cool belief).
How many cultures/countries in the world still officially use the dawn hour as the official start of the day? Not just special days, like religious feasts, but ALL days- as opposed to most cultures/countries who, in the modern era, probably use midnight as the official scientific start of the day (now that we have modern time-keeping capabilities).
And when people say “tomorrow” at 1 AM, they’re probably not thinking of the day as starting at dawn, precisely, but based on when they get up (or at any arbitrarily-chosen point during the time they’re asleep). For most of the year, I end up getting up before dawn, but still consider it a new day when I rise, not when the Sun does.
Can’t criticize anyone for using sunrise as the start of day. It’s kind of dumb to call the smallest possible length of time after midnight as the official start of the day but we keep using that system. I suggest 11AM should be the new start of day. Why not noon? I’m not going to sit around until lunchtime before I start getting nothing done for the day.
I’d guess the start of a new day is pegged to the middle of the night so that people who start off at different times don’t confuse things. Suppose we picked 6 am (average sunrise) as the start of the day. Then those who get up before 6 am to start work, go to the gym, catch a flight, etc. would be doing it during the “previous” day. Some time in the middle of the night seems best, and the dead middle of the night I guess has a certain logic to it. This is particularly true before the easy availability of artificial light that keeps many of us later these days. And that’s when the custom was started.
If I check my iPhone alarm at 12:30 am on Saturday night/Sunday morning before going to sleep, it may say “your alarm is set for 6:30 tomorrow”, where “tomorrow” means “Monday”. While technically correct, it doesn’t correspond to what any human would mean by “tomorrow”. There is a genuine risk of confusion if for whatever reason I did need to set an alarm for Sunday morning.
So at what time of night do we typically start to refer to the next period of daylight as “today”, rather than tomorrow? It’s certainly not midnight - for me it would probably be closer to 5:00 a.m.
I’d say if I’m up and not going back to bed (or my wife is up and not going back to bed even if I’m not up), I’d refer to the rest of the day as today. If I had to get up at 3 am to catch a plane it would be today. On a normal day if I got up at 3 am to use the bathroom, morning would still be tomorrow.
I can’t find a cite, and maybe it’s a meme from a western novel or movie, but I seem to remember the Native Americans’ method of determining “dawn” was something like when you could tell a black hair from a white one.
I agree - asking at what time do we start to refer to the next period of daylight as “today” doesn’t really make any sense to me. Because it’s going to depend - obviously, if I’m asleep between midnight and 6am, I won’t be referring to “today” or “tomorrow” during those hours.
Consider: you wake up briefly and check what time it is, and you are pleased to discover that it’s not yet time to get up and you can sleep some more, so you go back to sleep.
Scenario 1: it’s 1:30 a.m. Your 11:00 a.m. appointment is definitely “tomorrow”.
Scenario 2: it’s 6:08 a.m. Your 11:00 a.m. appointment is definitely “later today”.
The transition from “tomorrow” to “later today” will vary from person to person but I’m pretty sure it’s not 12 midnight.
Note that sunset as start of day is not just Jewish but is also Islamic and until all that not long ago even European.
This is why Christmas Eve started as the evening of actual Christmas day, not the night (let alone day) before.
Approximate noon is fairly easy to figure out if you use sundials (ignoring the equation of time). And once fixed length hours took over and clocks became a thing that made midnight simple. But it still took a while for Europeans to glom onto midnight as start of day.
Unless you’re an astronomer from a few hundred years ago, of course.
Sorry, I guess I wasn’t clear. Whether it’s “tomorrow” or “later today” depend on the circumstances (like @OldGuy said). If I’m sleeping from midnight to 6 am , it doesn’t matter when the change takes place - it’s at some point between when I fall asleep and when I wake up. Since I’m asleep, I won’t be referring to the next period of daylight at all . If I went to sleep at 4 pm and wake up at midnight because I have to be somewhere at 2AM , then 2AM is later today. If I wake up at 4 AM, whether my 11AM appointment is “tomorrow” or “later today” is going to depend on a few factors. Am I going back to sleep ? Then it’s “tomorrow”. Am I staying awake because I get up at 4AM every day? Then it’s “later today”. Do I want to go back to sleep but can’t ? It’s “later today”
Are you saying that Christmas Eve used to be the evening of December 25? I don’t think so. If the liturgical day started at sunset ( which is correct ) then Christmas would have been from sunset December 24 until sunset December 25. And you can still see remnants of this in Catholicism - you can fulfill the obligation to attend Mass on Holy Days and Sundays by attending a Mass after 4 pm the day before.
One non-standard definition of day I see is when measuring rainfall. Here (Australia) the rain day starts at 9am. Which means that overnight rain gets counted to the previous day.
If I’m defining time just for my own reference I tend to regard the day starting when I awake rested. Time does not exist in the depths of night as far as I am concerned. If I’m awake then it is because I’m sick and doesn’t count. It is some extra-chronal limbo.
If you look at old almanacs, it is apparent that while the civil day is defined to begin at midnight, the astronomical day begins at noon, while the nautical day ends at noon [I mean, the astronomical day starts just as the nautical day ends], for obvious reasons
Nope, midnight, as we do. There’s actually a statement in the Pandects (a collection of teachings by Roman lawyers that were used as a source of law in some European countries well into the 19th century) stating this as a matter of Roman law.
As to the astronomical day that begins at noon: There’s actually a very simple practical reason for this convention - it means you can record all observations that you’ve made over the course of one night under the same date.
Provided, of course, that you’re in a time zone that’s reasonably close to Greenwich.
(Astronomers around the world all use the same datekeeping system, in which the day number changes at noon UTC (i.e., Greenwich Standard Time, to within a few leap-seconds and such).)
