The writer had to attend a standup with a colleague in Norway to realize this and write an article. Funnily enough, as a Muslim I get reminded about this annually during Ramadan, which is right now.
First of Ramadan this year coincided with March 1, and it was a 12:45 hours of fasting from the first light of dawn to sunset at my
location, also near Los Angeles. Today it's going to be 13:15 hours long, and by the time last of Ramadan rolls in around the end of March, it will be 13:37 hours.
Ramadan is observed following the lunar calendar, which is shorter than solar- based calendars by about 10 days. A winter Ramadan is short and easy in the northern hemisphere and we will have the shortest days in 2031. 2047 it's going to be middle of summer, so the hardest.
In case you ask, well what about places where sun does not set? When do you have your Suhoor (meal before dawn) and iftar (breakfast meal at sunset)? Opinions differ, but people usually follow the more realistic time of sunrise and sunset at a reference location. My brother in law was in Sweden few years back and he used the time of Mecca as reference.
Living among Muslim and Catholic people in a time of simultaneous Lent and Ramadan, I first read "How the Fast Days are getting longer" and thought "How true, how true".
As a middle-aged human I first read "How the Fast Days are getting longer" as some kind of ironic commentary with the actual meaning being "how fast the days are getting shorter".
I think it speeds up because we settle in a routine, and when every day is mostly the same the brain just compresses the experience. The younger you are, the more new everything is around you, and you may not know yet what is worth trying or not, hence more things happen, and that makes it appear to last longer.
An interesting thing that non-muslims may not consider is that because Ramadan goes backwards in the western calendar approx. 10 days per year, for many people it'll be only a few times in their total lifespan when they experience and remember it being in the middle of summer and also in the middle of winter.
This. I was a high schooler when I had winter Ramadan. Next time that happens in 2031 I'll be 46, and 62 in 2047 when it's in the middle of summer. If I'm lucky I might get one more winter Ramadan in 2063 or something, InshaAllah
Yesterday I had a flight from San Jose to LA. I didn't really plan for Ramadan when I booked the flight. I was scheduled to land at LAX at 6.45pm, about 25 minutes before iftar LA time. The plan was to land, have something light at the terminal then drive 1 hour back to my place.
Well the flight got delayed about 25 minutes. It was going to land about 10 minutes after sunset. I was debating whether to buy something to eat before boarding. But then I can't have the tray open and eat when the plane is landing. I ended up breaking fast in the LAX terminal but around 30 minutes after I originally planned to.
Its really nice flying during sunset though, the pink sky around LA was gorgeous.
Depending on the specific school of fiqh that the commenter follows, he could have also been totally fine not fasting at all if traveling more than 80 km beyond his home.
That's right! People who are used to fasting don't want to miss out regardless. I mean you get the best type of food in Ramadan which for some reason people don't make the rest of the year.
As an Israeli, on Friday and Saturday the train/bus schedule changes based on the time Sabbath starts (which is, iirc, when 3 stars are visible in the sky), meaning that in winter there's like one or two trains really late (like 22:00-23:00) on Saturday, and in summer there's like four or five, starting at a more reasonable time than 23:00.
I saw some things recently about how Hakeem Olajuwon fasted during Ramadan and generally his performance was just as good during Ramadan as during the rest of the season, which is really impressive.
I'm not seeing how the time of sunrise and sunset differ according to whether your calendar follows the sun or the moon. Ramadan wanders through the solar year, sometimes occurring in the summer, sometimes in the winter, because it is scheduled according to the lunar cycle. But the fact that Stockholm has a lot more daylight during summer than Mecca does is just a consequence of the layout of the Earth. They both have summer at the same time. The effects are what's different.
If you use a solar calendar, the difference would only be by location. Solar calendar users already experience that. It applies for day-to-day stuff, but I actually can't think of any events explicitly tied to sunrise/sunset in a Western/Christian calendar. So you really need that to experience the full extreme, which Ramadan has.
Jewish holidays have that too, with the new day starting at sunset. But the calendar is lunisolar, so it wobbles buts doesn't drift. Islamic calendar has maximum differences.
That's why people who use lunar calendars tend to live closer to the equator, where the annual effects of the Earth's tilt are negligible and the lunar cycle is much more noticeable
Before the modern era, Christian countries also demarcated their hours according to sunrise and sunset; even today, Catholic and Orthodox monasteries and seminaries use these for the Liturgy of the Hours.
>Ramadan wanders through the solar year, sometimes occurring in the summer, sometimes in the winter, because it is scheduled according to the lunar cycle.
To be honest, that's the difference people are talking about (at least to my understanding). Because Ramadan follows a lunar calendar, the sunrise on the first day of Ramadan in Stockholm could happen anywhere from ~3:30am to ~8:45am depending on the year.
If I were using a lunar calendar as my actual calendar, the first day of the year would also have a sunrise time that varied significantly.
The start and the end of ramadan (the month) are based entirely on the lunar calendar, and the islamic authorities that your particular branch of the faith sighting the moon by eyeball, but the length of time per day that you're obligated to fast are based on sunrise and sunset, which is obviously solar.
I mean, yes the sighting of the Sun is a solar-related reckoning of time, but the solar calendar is based on the Earth's orbit around our Sun and the way that orbit changes the Earth's relative axial tilt in relation to the part which faces Sunward, yes?
On the other hand, a sunrise and sunset are not so much dependent on our orbit at all, but your particular latitude and longitude at any given point in time. Sunrise and sunset, in terms of orbital mechanics, aren't dependent on Earth's position in space or its orbit, but on the observer's position on Earth: where either the terrain/shadow obscures the Sun from our view or it doesn't. You can easily modify the phenomena of sunrise or sunset by traveling elsewhere, regardless of the solar calendar's season or our axial tilt.
Our solar and lunar calendars are reckoned by solar and lunar activity, and Earthbound Leadership adjusts those calendars so that they're calibrated to that activity. On the contrary, with our civil time fixed in an abstract 24-hour cycle and sliced up into 60-minute time zones (give or take), sidereal time is sort of divorced from clock time, and we rarely attempt, in modern times, to calibrate civil time according to the Sun's actual meridians at all -- but we do, in fact, find it necessary to compensate for variations in the Earth's rotation.
Ask any astronaut about sunrise and sunset, because for a satellite orbiting Earth, the Moon, or a probe which is traveling somewhere, those are alien or malleable constructs.
I mean, very roughly, our western calendar based on solar observations is consistent in that the same months will always be in the same season. You can always expect that January and December will be cold, and in the northern hemisphere have some of the shortest days of the year.
The Arabic Islamic calendar is not like that. Ramadan is one of the standard months of the lunar calendar and depending on what year you're talking about, Ramadan might be exactly in the middle of summer, or it might be in the direct middle of winter. Very approximately it goes "backwards" in seasons 10 or 11 days per year and eventually wraps all the way around from the POV of the western solar calendar.
In the western calendar, the winter solstice will always fall on December 20th or 21st even going up to the year 2100. And the same for the summer solstice on June 20th or 21st.
Yes but you said that "sunrise and sunset are solar reckoning" and I wasn't taking issue with the topic of lunar/solar calendars because calendars don't count off or delineate the hours in a day.
Every calendar that I'm aware of considers "days" as an abstract unit which consists of one planetary rotation, without nuances of activity or visibility of external bodies, right? True?
What I meant was that for an observant Muslim, the month start and month end date of Ramadan is set by the moon, but also each day has a very slight different sunrise time and Iftar time (sunset, when you can eat and drink again) which is dependent on the sun's position.
You are right that the human perceived calendar date is something we invented rather arbitrarily. Of course, the longest day of the year was occurring on June 20th before humans invented agriculture or cities. That we call it "June" and "20" is a cultural artifact.
Sunrise and sunset are wholly dependent on the observer’s position because “night” is a cultural construct referring to being within the Earth’s shadow rather than a dragon devouring the Sun, yes?
I am heading to the local cafe right now. This is the only time of the year they make Special Ramadan Phirni and they don't even share that exact recipe. I have begged them many times: either make it year round or for just give me the bloody recipe.
In Bangladesh we also make a bunch of different dishes only in Ramadan. I mean they are made all year round in restaurants, but in Ramadan every Muslim household and street corner vendors will make them- haleem (lentil soup with meat), piyaju/beguni (deep fried snacks made of onions, lentils and eggplant etc.), bundia/jalebi (desserts), sola-muri (chickpea dish with puffed rice), "rooh afza" beverage to name a few. Even my non-muslim friends would crave some of these dishes and look forward to Ramadan to enjoy these.
How apropos and now I'm curious how many English speakers don’t really consider how a “mildly profane” adjective had its start as a blasphemous slur against the Eucharist and a certain Queen?
When living in Stockholm, I came to appreciate the various levels of twilight and darkness, rather than thinking of day and night so strictly. The sun being low on the horizon also scatters light across the sky in ways that are very beautiful and last much longer than sunrise and sunset in Australia where I grew up.
Having grown up around the same latitude as Stockholm, one thing I never realized until last year when visiting tropics is how my subconscious associates warmth with long evenings. Being used to summers where you could basically read a book outside at 11PM, it felt really weird to be outside in tropic heat, but complete darkness by 6PM.
Catches me every time too. And it's so quick. You can go in to a shop to pick up a packet of crisps thinking it's daytime, but actually is quarter past 6, so you come back out and it's full dark!
I'm in the southern UK, and I'd take our late-May/early-August "it's light while I'm awake and dark while I (should be) asleep" all year round if I could get it.
You could become peripatetic and seek out the spot of opposite latitude during the dark season. So you could have 15 hours of daylight, 12 hours of daylight, then 15 hours of daylight again. I've thought that with idle rich amounts of money I'd get a very large yacht and sail the pacific rim in time with the seasons, perpetual spring, summer, spring, summer.
We have different definitions of rich. It's not just the cost of living. It's also the time and to deal with the governments to allow this, it's having the money to spend the time, it's the job that allows this, it's the time away from family not being catastrophic for someone's wellbeing. Frankly, this is vastly infeasible for 99% of people. I'd easily consider the remaining 1% "rich" in some way
The first time I visited the tropics, I never realised how much I associated the dark with it being cold!
We went for dinner in the afternoon, sun was up, it was blazing hot, everything normal so far. We had dinner while the sun set in a nice air-conditioned restaurant, so it was dark when it was time to leave, and I walked out into the tropical night and was so confused why it was still warm and moist outside!
Similar experience for me but probably even more extreme.
I'm originally from São Paulo, Brazil, the Tropic of Capricorn almost cuts through the city itself. Sunrises and sunsets are very quick events, sitting somewhere to watch it would take some 30 minutes, and then darkness.
Even after 10+ years of living in Sweden I still get mesmerised by sunrises and sunsets here, they last for so long and I get to be awed by the changing of colours, shadows, shapes, for hours. It's one of my favourite things to do during summers, just to be out somewhere by a lake with some friends, having food and drinks, and watching the endless twilight.
> When living in Stockholm, I came to appreciate the various levels of twilight and darkness, rather than thinking of day and night so strictly.
In Chile you get somewhat long days and short days too, especially in the south, but instead of trying to be super precise about sunlight, the afternoon and night blend in and sort of crossfade. You end up with "8 de la tarde" (8 in the afternoon), and "6 de la noche" (6 at night) depending on the season.
7/8/9 de la noche (vs tarde) is used by 60/97/100% of American Spanish speakers vs 1/16/97% of European Spanish speakers. I wonder if the difference is due to Spain's generally late sunsets.
It would be interesting to redo this analysis with a corpus that indicates seasons though.
I think I have used "8 in the afternoon" even as close to the equator as Atlanta (~34 N). Our latest sunset is 8:52 pm, surprisingly late, because we are very far west in our time zone.
The whole "6am sunrise and 6pm sunset every day of the year" thing at the equator is kind of mind blowing.
Another maybe counterintuitive fact is that (to a reasonable approximation) everywhere on earth gets the same number of hours of daylight over the course of a year.
Funny because growing up in the tropics I thought sunset and sunrise were synonymous with those times of the day, and learning people in other parts of the world experienced shrinking/lengthening day/night cycles was mind blowing. You mean it's 8PM in the night but the sun's still in the sky?
I was at a wedding in Sweden near midsummer with a lot of international guests. They were quite surprised to get out of the reception dinner at 10pm and see that the sun was still up. We were below the arctic circle, so no midnight sun, but it doesn't really get dark during the night, you get an hour or two of twilight, and then the sun rises at 2am again.
I travelled to Stockholm from North America a few decades ago, right around midummer. Worst jetlag of my life.
The problem was that 20 hours of daylight, especially having 2:30 AM feel like 6:30AM. It was impossible to get an adequate amount of sleep. The paper thin curtains in the cheap hotel where I stayed did nothing to block out the light.
If I am ever in that part of the world at that time of year again, I will be bringing a sleep mask and seeking out a hotel with proper blackout blinds or curtains.
You can just bring or buy some pop-up travel blackout blinds made for babies. We used those with great effect when visiting my parents' summer house in Northern Norway in the summers when the kids were young.
Bonus, they now work as great blackouts in my home office for video calls when I do not want sunshine and clouds to change my green-screen effects etc.
I would have thought that for places that close to the arctic circle would be a national crime to not have full black out curtains. The difference being the punishment based on what nation the crime was committed.
I live in the south of England and experienced this in Scotland. I was trying to get somewhere to pitch my tent but rapidly running out of light, or so I thought. It was the height of summer and it just never really got dark. Maybe England isn't as different as I think it is, but it was strange to find my assumption that night=dark was quite wrong.
> The whole "6am sunrise and 6pm sunset every day of the year" thing at the equator is kind of mind blowing.
You can take this further. Look at weather and seasons. Here's Nairobi's yearly averages[0]. You can see that both temperature and precipitation are fairly consistent. On the other side of the continent Libreville[1] has a bit more precipitation variance but still low temperature variance. Let's got to South America with Macapa[2] and Quito[3] and let's keep going and land in Kuching[4].
Essentially in these regions, there are no real seasons. At least in the sense that many think of them. Things do change, but winter isn't that different than summer.
I know there are variances, but the scale masks a bit of what's going on. So let's look at London[5], Osaka[6], Auckland[7], Los Angeles[8] (often joked at for having no weather), Seattle[9], and Oslo[10]. As you can see, these are extremely different situations. It even has large effects on how people think about weather, time, and other things.
It's funny how what is so obvious and normal to some are completely different to others. Sometimes seeming as if we live in different worlds. In some sense, we do, and I think we often forget that.
There is the same number of hours of daylight, but near the poles you sleep through a lot of those hours in summer. So you experience far fewer hours of daylight.
Another mind blowing thing about the equatorial sun is seeing it above you! Where I grew up, the sun is never higher that 30 degrees.
I lived in East Africa for a while and you’d get kick out of the way time is referred to in Swahili, “midnight” is 6am, and the first hour of the day 7am etc. makes a ton of sense when sunrise is around the same time each day!
Yes, though a location at 45 degrees N/S only gets 70.7% as much sun power per area due to not being perpendicular to the sun's light, and even less on the ground due to extra atmosphere to pass through.
Appropriately enough, that "everywhere on earth gets the same number of hours of daylight" fact came from a solar system salesperson, who didn't go out of his way to emphasize the atmospheric effects here at ~49°N.
The silver lining is that our longest days are often our sunniest.
> Another maybe counterintuitive fact is that (to a reasonable approximation) everywhere on earth gets the same number of hours of daylight over the course of a year.
Not the same amount of usable daylight though as the amount you have to waste to get a decent amount of sleep all year around varies by latitiude.
Living at the equator most of my life, it's actually funny how schedules are messed up when the sunrise is half an hour earlier or later. Traffic becomes chaotic because some people insist on getting home before sundown, or things like people becoming uneasy that the school starts before sunrise.
Weather is fun too, because it changes by +/- 3 degrees throughout the year. The heat makes my bedroom door expand. We had an argument with the housing developers because we had custom doors that didn't fit. But turns out it was passing all the tests when they ran it, and not in hotter periods of the year.
When we were in Hawaii I think the only reason we caught the sunset is because we were less than 400 yards from a beach. By the time you know the sun is going down you are about to be in the dark.
Movies about vampires in the Arctic Circle are fun but vampires at the equator would be more terrifying for the humans at dusk and for the vampires at dawn.
There is a handy rule of thumb called the "rule of 12ths", used in seamanship / ocean navigation / tidal calculations (maybe it is used elsewhere too, this just happens to be where I recognize it from). I think it can apply to solar, seasons, etc. -- well, anything sinusoidally cyclical -- as a useful mental model:
If you divide half the phase of a cycle (peak to trough) into 6 hours duration or whatever appropriate unit, like 6 months, i.e. x-axis --
then going down from the top of the peak (or up from trough), the amount of y-axis change in each unit/hour is:
Hour (or month #): amount of change vs. peak-trough total (i.e. total = 2*A)
1: 1/12
2: 2/12
3: 3/12
4: 3/12
5: 2/12
6: 1/12
For us, the peak / trough are: June 21 to December 21, and the x-axis is 1 month units. And assuming maybe a 2 hour peak-to-trough difference in daylight time y-axis (depends on latitude you live of course), then each 1/12th equals 10 minutes.
So these days (late March) we are in the middle of the fastest decrease part, and each month we gain 30 minutes of daylight. Or, each day we are seeing sunset get pushed by like 1 minute.
"One of the more interesting features I hadn’t appreciated before is that when you get close to the Arctic circle, the length of the days is essentially a zigzag, straight up from the winter solstice all the way to the summer solstice and back down again."
I had noticed this too and wondered if it was exactly true, with the "zigzag" being straight lines - I thought there might be a simple proof of this fact based on some trig identities. There's not, because it's not true - the lines aren't exactly straight, even if you ignore solar refraction - but it's a very good approximation.
The calculated daylight even downplays the actual light at the high (or low) latitudes quite a bit. E.g. at latitude 60 there's a "nominal" midsummer night of about four hours, but it doesn't really get dark, as the light from the refraction is quite strong even with the disk not being visible.
That's called "twilight". In the section "Atmospheric refraction and the solar limb" there's a modified sunrise equation with a variable "a" and text suggesting a correction of 50 minutes of arc there.
If you replace 50 minutes with:
- 6 degrees, you get the times of "civil twilight" (roughly speaking, when you don't need light outside). At 60 degrees north at midsummer the minimum altitude of the sun will be about -6.5 degrees so almost all of the nominal night is civil twilight.
- 12 degrees is "nautical twilight" (horizon clearly visible)
- 18 degrees is "astronomical twilight" (sky is dark enough for all astronomical observations).
(It's possible that those are defined as 6 degrees + 50 minutes, etc.)
And it's not just "sunset + X minutes" where X would be a constant. In the winter this X is much shorter than in the summer.
For me X is then a "travelling" value which in the winter is at 1/3 between sunset (0°) and civil dusk (-6°), and in the summer it goes up to 2/3. Calculated as the moment when the blinds go down.
You made me check the code and actually I have it the other way around (and with different ratios, winter=-6°, summer=-2°), because else the blinds would go down too late in the summer (after 22:00).
Twilight is caused by scattering rather than refraction. There's sunlight bouncing around in the atmosphere, keeping the sky non-black even after sunset.
I just pulled up Whitehorse, Yukon (at the 60th parallel), and sure enough, the longest day of the year is essentially always day: https://www.timeanddate.com/sun/canada/whitehorse. Almost 5 hours of civil twilight, but civil twilight is still daytime in my book.
Even during the "night," the sky stays illuminated enough that it never truly feels dark. It definitely challenges the idea of what nighttime means and makes the summer feel almost magical, but I imagine it can also mess with your sleep patterns!
Not exactly; even after the sun is fully below the horizon there's some light. See the interactive graph - the times aren't long enough for twilight. But you can use a larger value of "a" in the equation above it to make that change.
I'm from Iceland, so a latitude of about 64.15 or so. The extremities of the graphs kind of describe how the mood of the people swings up and down all year round. In the middle of summer, around the summer solstice, people are bordering on mania, enjoying endless daylight and trying to get the most out of each day. As winter solstice approaches, everything becomes more subdued, a bit depressed even. It's often a bit difficult to live with, especially during the shortest winter days, but the summers are so incredibly amazing that it feels like it's all worth it.
The seasonal extremes of daylight are so extreme up here in Finland that the cycle of night & day seems a bit less like a 24-hour cycle and a bit more like a 365-day cycle.
An artifact of this is that my 5yo might not see a dark sky for the entire summer, unless we keep him up awake for the traditional Midsummer hangin'-out.
Coming from middle of Sweden I remember the first time I spent a midsummers night in Lund in the south if Sweden and was astonished that the night was in fact dark! In my hometown, well below the arctic circle, the month of June is still constant daylight.
I've been using my iPhone in standby mode at night and I have the world map with the daylight "sine wave" on. Its been fun watching the shape of the daylight region change as it get closer and closer to the top of the map. After the equinox it pops through the top of the map and then it's upside-down for the next 6 months.
Watching the changing shape of the daylight illuminated portion of the map over the year has given me a much better understanding of what the equinox means, why daylight hours shift, and just in general a better appreciation of our place in the solar system.
DST really bothers me. I actually have a wall clock set to local solar time, so that I can quickly see what time it "really" is. For some reason I've always been very sensitive to when sunrise and sunset is, and having them offset makes my brain feel weird.
An interesting analysis, covers a lot of ground, but no mention of the "analemma" (https://en.wikipedia.org/wiki/Analemma), an annual figure-eight curve that results from earth's elliptical orbit around the sun, and that must be included for reliable calculation of solar position and rise-set times.
Calculating the analemma requires multi-term Fourier analysis to reliably pin down the sun's position, without which nautical sextant calculations would fail. Even in the GPS era, professional sailors are required to (demonstrate their ability to) turn sextant sightings into geographical positions, against the possibility of a high-tech failure.
Apropos, during my around-the-world solo sail (https://arachnoid.com/sailbook), because of just such an equipment failure, I was obliged to navigate from French Polynesia to Fiji using a sextant -- and reliable solar positions.
I live just a couple hundred miles south of the arctic circle, and personally I hate the time of year where we "accelerate" into the equinoxes (equinoxii?). The rate of change is just too fast and too disruptive, and you _really_ see its effects on people. And then DST comes in and makes it even worse.
The difference as you climb in latitude is really shocking. Even just another 3-400 miles south of here, the rate of change is way less severe.
Anyway nice work and cool article! I've done some of these rough calculations myself before to plot out the change just to verify that I'm not insane for hating this time of year, and you did a way better job than I ever did :)
I grew up here, so it's "home" so to speak. Well, technically my childhood home was a few hundred miles further south than where I am now (Fairbanks, Alaska). It's definitely an extreme climate to live in, but there are a ton of things to do outdoors, and although the daylight changes are very extreme, the excessive summer daylight makes that part of the year truly amazing.
I do think the extreme polar opposites in daylight and temperature for summer and winter solstices contribute to people here being a little...unbalanced. But for a lot of people, the unique landscape, low population, and abundance of outdoor activities make it worthwhile.
Something that is still crazy to me, regarding time zones, is that my hometown (where my mom lives and we visit frequently) is about 1.5 hours to the west, one timezone over.
When I’m taking to her on the phone in the evening, we’ll be talking about it getting darker.
The difference in the sunset 1.5 hours away in another timezone:
About 9 minutes.
This equates to my evening daylight lasting 51 minutes than hers, and her daylight in the mornings starting 51 minutes before mine (in our respective time zones).
Which seems to negate the whole effects of daylight saving time for one of us.
Of course this is exacerbated even more if you’re across the border of a timezone from each other (which I pretty much live on the western border of ET).
Play with timeanddate.com's times. It gives the total amount of civil twilight for the day (which is split in half). For example at Atlanta (https://www.timeanddate.com/sun/usa/atlanta) there's 58 minutes per day at the summer solstice, 55 at the winter solstice, and 50 at the equinoxes. As you go poleward those numbers increase but it's always summer solstice > winter solstice > equinox. This is basically down to the angle between the sun's path and the horizon and I think I get why that would be different in summer than in winter but I can't get my head around the fall/spring bit.
I think the angle under which the sun rises/falls is steeper in spring/autumn. And summer/winter is less steep. And in summer it bends upwards when under the horizon, making summer sunset longer than winter. I'm not sure if these are the right words - it sounded better in my head!
You'd be able to do it based on the math in the article. Civil twilight lasts from sunset until the Sun is 6° below the horizon. So in the spherical law of cosines in the article, you'd just set a to be -6° instead of 0.
I have a wake-alarm[0] that triggers 30 minutes before civil twilight, that is roughly 60 minutes before local sunrise.
In the northern hemisphere at 52 degrees it gets earlier by about 2 minutes each day (additional 4 minutes of daytime).
So I get more sleep and short days in winter and less sleep and longer days in summer. It's liberating basing schedule on it and not some arbitrary time.
This phenomenon became very interesting to me after moving approximately 14 degrees further north (on the northern hemisphere) and experiencing not just shorter and longer days, but more rapid changes in day length during spring/fall.
The impact this has on daily life is larger than I had anticipated, and in general reducing the intensity of the cycle is a selling point for cities closer to the equator. It’s been nine years since my migration north, and I’ve only moved further north so this isn’t a deal breaker for me. It’s mostly something from my childhood and young adulthood that I took for granted. I’m now eagerly awaiting the day when my normal waking time is during dawn, which should be in early April.
I’m still significantly further south than Northern European countries mentioned in this thread. Maybe life has more moves north for me in store.
Very interesting discussion! I did a less theoretical approach a while ago to calculate the same thing: I just go to timeanddate.com, find the city I'm interested in, go to its sun page (example for New York https://www.timeanddate.com/sun/usa/new-york), and find the table that shows the difference in daylight minutes per day. No math or programming needed, just copy-paste and some buttons in Excel.
Not as satisfying as a derivation here, but a quicker way to get the answer.
EDIT: I did a spot check for Rovaniemi, Finland. This city is far north enough that the sun is up all day (66.5 degrees). But the graph on this page seems to be a little bit off: it requires an even higher latitude for that to show up.
Moving to Northern Canada has made me really really appreciate Spring. Going to work in the dark then going home in the dark is exhausting. I'm at 56ºN. I imagine it's worse for those who are even further North.
Do the maths for the southern hemisphere and compare: It is my belief due to axial tilt AND the solar rotation period and solar distance, the effects aren't entirely equal north and south pole.
Do the maths for the dusk side of the story. Dawn is good, but how this behaves in the rate of sun appearance and rate of sun disappearance also has a shift, the two event peaks aren't aligned. Again, a function (I believe) of the axial tilt.
So its a system with differences, with multiple inputs, with complex maths. I love it!
Fasting the month of Ramadan when it lands in March or September is always the most interesting for this reason. You have to change how you plan your daily routine as the month goes.
This is surprising. I had always assumed that the length-of-day function is essentially a sine wave everywhere on the planet, and that the derivative would thus be another sine wave shifted by 90 degrees.
When the day length is maximal/minimal (solstice), the day length change rate is near zero, and vice versa. That's still true in the more accurate model, even though the shape of the functions is more distorted.
> On the equator, every day of the year is exactly 12 hours long
But surely that is not true, as the Earth's rotation is tilted. Is this supposed to be a year round average? Despite calling out more advanced corrections one can make, this doesn't seem to be mentioned anywhere?
It's true. Highly recommend getting a globe in your hands to convince yourself about stuff like this. Close one eye, pretend you're the sun and observe the effect the tilt has and how it has no effect on the equator (apart from changing the angle of the sun; interestingly the sun's path alternares between being in the north sky and being in the south sky).
You'll also be able to understand time zones and great circles (flight paths) better with a globe.
It's true that the Earth does not usually take exactly 24 hours to rotate, it's only 24 hours on average over the course of the year. However, the difference is only ever off a few seconds at most. Those seconds pile up across the days around perihelion and aphelion amounting to several minutes cumulatively but that doesn't affect the length of the day, only the amount that solar noon differs from noon on the clock.
The reason that days are a few minutes longer than nights at the equator is due to atmospheric refraction which makes the sun visible a little before it actually has "risen" and similarly, keeps it visible a little after it has "set".
In Garissa, Kenya, which is almost exactly on the equator, the day length varies between 12 hours 6 minutes and 12 hours 9 minutes. So it is 12 hours if you are rounding to hours.
Pontianak in Indonesia is right on the equator (I'm seeing 1 minute 14 seconds south latitude at Wikipedia).
timeanddate.com gives (https://www.timeanddate.com/sun/indonesia/pontianak) variation between about 6.5 minutes and 7.5 minutes above 12 hours, long at the solstices and short at the equinox. The difference is due to the sun setting vertically at the equinoxes and at a slight angle to vertical at the sunset.
I'd say the graph's qualitative behavior is correct. Once you get to the arctic circle, there are singularities in the rate of change of the length of daylight.
For example, if you're at the North Pole, the sun is below the horizon all winter, and then on the vernal equinox rises above the horizon and does not set again until the autumnal equinox. So, formally, the rate of change in daylight is zero all year long, except on the equinoxes when it is infinite. Any latitude above the Arctic Circle will have these kinds of singularities.
In practice there are some corrections to the amount of daylight that I discuss at the bottom of the article, the most important of which is the effect of atmospheric refraction. If you were standing on the North Pole, you'd actually observe the Sun appear to rise some time before the vernal equinox.
The graph looks like it's straight up interpolating between a sine curve and a tangent curve, it's so cool that way. (The calculations are more involved than that).
Also signal analysis people will enjoy this natural system producing "almost pure" triangle and square waves. Nudge the plot to 66.55 degrees and it's at the most triangle wave point. :)
The opposite also happens, where the sun is below the horizon for months or weeks, and at the end of that period, it will inch towards the horizon, and you expect sunrise, but nope, it'll move furrther again... of course there'll be twilight (followed by night), but you might not see the orange ball of bright light for weeks or months.
Here is a physical 3D visualization (a LEGO set) showing the sun and moon orbits. My children and I put this together last year before the eclipse as a way for them to better understand why the eclipse was happening
In the set, the earth spins on its axis, the moon orbits the earth, and the earth orbits the sun. There are stickers that mark the months of the year so you can see when solstices and equinoxes happen.
I find the more frustrating / noticeable the equation of time for a given point, where solar time and local time diverge, day to day it feels very counterintuitive, but when you see the chart it makes complete sense…
Yeah I have to say the north of Europe is bad folks. Winters are terrible. You just go to work/school in the dark and come home in the dark. There’s also less snow now than twenty years ago which means even less light.
In the summer it’s light outside for more hours than you are awake. Okay wow, so what? It’s a nice novelty. But it doesn’t make up for it. Not remotely.
Midsummer is a sad time because now I know that I will lose X minutes every day of light.
Using DST is just the extra bit of small cruelty on top of that.
DST only really makes any sense at mid-latitudes. If you go close enough to the poles it just seems silly to move around that hour - does it really matter if the sun is up from 2 AM to 10 PM or from 3 AM to 11 PM?
DST is completely silly as far north as the Nordics. The rate of change in daylight is so rapid around the equinoxes, that the effects of DST are erased in less than two weeks. It's completely useless.
Screw half measures like DST, as an office worker I have a dream of working in winter from 16:00 till 24:00, sleeping from 01:00 till 09:00 and enjoying my sunlight for the rest of the day. I would fit right in working remotely for a company somewhere in the Far East.
Of course, the worst part is that often in winter we don't get sunlight at all, only a gray-ish cover of clouds in the sky :(
I’m in the Netherlands (around 52ºN) and in my opinion DST is counter productive, especially considering the effects of global warming.
Summers are getting hot, to the point where it’s uncomfortable to be outside while the sun is out. It’s barely tolerable in the shade, assuming you don’t move too much. It only gets comfortable outdoors after sunset. During workweeks this means you barely have any usable outdoor time before you need to go to sleep. It also means your bedroom has little chance to cool down before you need to go to bed. Summer nights are nice when you’re outdoors, but DST robs us of the best hours to be outside.
If we’re going to move the clock in summer, we should move it backwards another hour. It would mean 2 more hours (compared to the current DST) of nice summer nights, instead of extra hours of scorching sunlight. I suggest we call it ‘Moonlight Saving Time’.
Shortest day where I currently live has 5h49min of daylight. My childhood home had full month of no daylight. You definitely have shortage of daylight as you move towards poles.
I knew days lengthened quicker around springtime, but your interactive visualization and clear breakdown of the math behind it makes this phenomenon tangible
While southern Florida is hardly at the equator, living here has really highlighted how northern-hemisphere and temperate-centric the online sphere - tech in particular - tends to be.
We don't get spring/summer/autumn/winter so much as rainy and dry season; heat pumps are irrelevant; natural disasters come in the form of hurricanes, and weather is either sunny or stormy; the days don't change in length much; and so on and so on.
It's a bunch of little things, but it's been surprising to me how often they come up in discussions, and just how rare (sub)tropical-specific problems and topics are in comparison. It makes me wonder what it's like to live somewhere even further removed from the natural world of the north.
It's always interesting how it affects how people think about the day. If you look outside and it's dark then it's easy to think that the day is basically over, even though the time might say otherwise.
I really appreciate the long winter nights and long summer days in Norway. Being able to wake up to the sun as early as 04 and enjoy it until after 23 is great, and the UV is only high during the middle of the day. Long summer days are awesome. Long winter nights are probably not as appreciated, but I enjoy those too.
Fifteen years ago, I moved from Orlando to Seattle, and almost 20 degree change in latitude. On top of that, Orlando is famously hot and sunny and Seattle famously cold, cloudy, and rainy.
Despite that huge change, I adapted to the new climate just fine. I don't mind the gloom or the cold. The six months of gray skies don't get my down like they do a lot of people.
But even after a decade, I still haven't gotten used to how much the day length changes. Every summer my brain keeps expecting the sun to go down any second now while it sits up there near the horizon giving an extra two hours of daylight. Every winter it feels like the sun disappears too early.
It’s rarely super hot or super cold like a lot of places.
You get these ridiculously long summer days that last forever. It’s perfect for athletics and hiking and spending time on the water.
And likewise you get these wonderfully wet and dark winters which are perfect for life’s other joys: coding, reading, playing video games, boardgames, drinking coffee, etc.
I love places like San Diego / LA but I wouldn’t want to live in a place that is always a perfect summer day.
I was in Seattle Sept-Dec of 2008 on an internship and I remember feeling some of this. Based on what people had said, I was geared up for four months of a soggy, misty mess, but it wasn't that at all— the autumn there was splendid, with tons of breezy, cool days where the sun still shone, with the trees around my place in Madrona showing brilliant colour for weeks on end.
I love 4 seasons. But the weather and day length make for a difficult half-year from Oct - Mar. The NE corridor has some of these traits, but it was a lot easier to deal with there. In the NE, rain & grey-skies aren't as persistent. In Seattle, a month can go by without seeing the sun.
That's much of the west coast (west of the cascades). I moved from Seattle to the Bay Area, and it's basically the same weather except somewhat shorter summer days and winter nights, WAY more sunshine, and generally about 10f warmer. Except in the summers where these days it seems like Seattle has more 95+ degree days than the peninsula does.
The downside of the historically mild climate is a lot of older homes weren't built with energy efficiency in mind and now in 2025 we have to deal with that inefficiency on our energy bills :'(
I think what's fascinating about it is the daylight changes you experienced in the 20 deg latitude change you experience from Orlando to Seattle are dwarfed by the changes from a ~15 degree latitude change from Seattle to Anchorage. By the time you're getting close to the pole, you can see huge differences in solstice minimum/maximum sunlight by moving just a few hundred miles north or south.
It's the same in the UK vs Southern Europe and Japan where I've lived before. People complain about the wet weather, but it's not that IMO what really gets to you, it's the dark winters with so little daylight compounded with the abundance of cloudy days.
Temperature-wise, most of the UK is actually quite moderate compared to central Europe. It's winter darkness that gets to you.
Yeah, I hate it. I don't need more light in the morning, I'd rather have that as a bit more visibility when skiing after work. And it anyways only takes like two weeks before the gained light in the morning is gone.
25th of october day is from 08:21-17:39,
26th of october from 07:24-16:36 after dst,
and then 17th of November we're at 08:19-15:43 (so back to dark mornings). I'd rather the 17th have light until 16:43.
Could be so the time is better synchronised with the rest of Europe, which is relevant for business reasons. I seem to recall reading recently about some other country doing exactly that (though it wasn’t Norway).
Mexico used to have daylight savings even though they're close enough to the equator that it doesn't make sense - that's to harmonize with the US. When they did have daylight savings time, though, the state of Sonora didn't, because it borders Arizona, which doesn't.
I'm trying to find the darkest corner of the earth to chill in so I can actually get some work done. I can't get anything done when the sun is out and people are out and about. Maybe I'll move to that Italian village that has the giant sun mirror thing.
I personally like extremes. My ideal scenario would be a dark room where I can get work done, and then every hour or so, I take a five-minute break outdoors in direct sunlight.
I spend most of the day in a fairly dark room, but make sure to get at least 20 minutes of sunlight on my bare skin and eyes every other day -- but it's not because I like extremes: it is because sunlight is good for me, but LED light bulbs are bad for me or at least they are if they are of typical brightness and they are on most of the day.
July - September, yes, we have oppressive sunshine.
Spring/fall tend to be cloudy & rainy, and November to February-ish is referred to as "the big dark" - the days are short and the sun is low and obscured by clouds when it's above the horizon. Sounds like you'd get a lot done then (as do many people here).
Calgary, AB enters the chat:
Calgary, Alberta, is considered the sunniest city in Canada, with an average of 333 sunny days and 2,396 hours of sunshine annually.
I live at ~64 deg latitude in the USA (Alaska) and 100% agree with everything you said. The timing of sunset has such a profound effect on when you consider the day "done". In Dec it's painful to haul myself outside at 5 or 6 PM since it's "night time" already. Meanwhile in June, at 11PM/23:00 when it's still bright out I have to remind myself to home and go to bed so I'm not a tired wreck at work the next day :)
I really struggle with this at daylight savings switches when I work in offices where I can see a window. It takes me a couple of weeks to adjust. In one direction I find I work later than I intended. In the other direction I find myself ready to leave and realize it's only 4:30
My buddy went to Norway and was super upset because the sun never set in the part of Norway he was staying in and he had no idea it would be daylight almost the majority if not the entire day. He also said his Norwegian family was getting upset with him because he wasn't sleeping and keeping everyone up due to his lack of day/night reference.
July 5th through September in Seattle are a dream; incredibly long days, dry but not too hot. The sun never sets. I've been a lot of places on the planet and PNW summers are uniquely great.
However, during the winter it's dreary, it's dark by noon, and every year around October the raven comes tapping at my chamber door.
July of 2020 I left and went south to Central America. That first 'winter' I kept waiting for my annual S-A-D season to start. It didn't. The second 'winter' was worse because I reasoned the lst time could have been endorphins keeping me going. I was really expecting any day for the depression to start. And again, it didn't. December and January felt normal. That very consistent 7am it's bright sunny day and at 7pm it's dark night all year is helpful.
Quite literally, I never intended to return to Seattle, but with the recent economic turmoil it worked out that way. S-A-D season kicked off like usual, even with the 10,000 IUs of Vitamin D.
Without a job I moved to Eastern Washington, and within a month I was doing better, life got easier and the future was far less inscrutable. I have the energy to do the work, and after an angry or sad thought the follow-up thought is "that was a bit dramatic". That's a sign every year that things are on the up-swing.
Many people love and appreciate the Seattle climate just as it is; I don't know really anyone that reacts quite as severely as I do to it. Not being in Seattle weather means I get 6 more months of life every year. It kills me how much time I wasted trying to 'fix myself' in a place I just wasn't meant to be.
I've only ever been to Seattle to visit in summertime, and largely agree with everything. It's probably the prettiest place I've ever been (weather/greenery wise). But I already know I can't handle the greyness of the other seasons. Real shame.
Even living in the south, the 3 or so months of SAD feel like an eternity. I don't know how anyone could stand an even longer period.
I live within a short distance of the western side of the Cascades (I don't want to dox myself any further). Meaning I'm on the eastern side. The difference in weather between the two sides is pretty shocking. During the winter, I often look to the west and see a solid sheet of clouds.
The western half of the state is close to the ocean with warm ocean currents, so you get a lot of moisture. However the Cascade Mountains split the state N and S. Windward side is Seattle side, so all the rain stays there.
Eastern Washington then is in the rain shadow. Actually I think it's high desert - there's very little annual cloud cover.
The Cascades go all the way to California so this pattern applies to Washington, Oregon, and maybe Nevada.
In the context of my original comment, I can only speak from an experiential sense. I think it's the strength or frequency of the sunlight, maybe the UV, is what makes the difference.
We have this same pattern in Vancouver and a good chunk of British Columbia as well, though this winter which just ended was the mildest of the 11 years I've been here
First of Ramadan this year coincided with March 1, and it was a 12:45 hours of fasting from the first light of dawn to sunset at my location, also near Los Angeles. Today it's going to be 13:15 hours long, and by the time last of Ramadan rolls in around the end of March, it will be 13:37 hours.
Ramadan is observed following the lunar calendar, which is shorter than solar- based calendars by about 10 days. A winter Ramadan is short and easy in the northern hemisphere and we will have the shortest days in 2031. 2047 it's going to be middle of summer, so the hardest.
In case you ask, well what about places where sun does not set? When do you have your Suhoor (meal before dawn) and iftar (breakfast meal at sunset)? Opinions differ, but people usually follow the more realistic time of sunrise and sunset at a reference location. My brother in law was in Sweden few years back and he used the time of Mecca as reference.