Got the Sunrise and Sunset numbers for today from MSN Weather:
Gemini AI:
Why is my weather app giving me a day of 12 hours and 14 minutes. By my calculations, it should be 12 hours 15 minutes?
Your simple math (6?PM to 6?AM or direct subtraction: 18:53−06:38=12 hours 15 minutes) misses how weather apps calculate daylight duration and how rounded UI times work.
Why the 1-Minute Discrepancy Happens
Rounding of Displayed Times: Weather apps often show rounded or truncated time values for sunrise and sunset (e.g., displaying 6:38 and 6:53), whereas the internal calculation uses exact seconds or fractional minutes (e.g., sunrise at 06:38:22 and sunset at 18:52:38).
Definition of Sunrise/Sunset: Daylight length isn't just center-of-sun geometry; it factors in atmospheric refraction (bending light over the horizon, adding ~2–3 minutes total) and whether the app defines sunrise/sunset by the upper limb (first/last edge touching the horizon) versus the center of the solar disk.
Truncation vs. Rounding in Duration: Exact raw difference might compute to something like 12h 14m 18s, which software either truncates down to 14 minutes or rounds.
Quick Verification Check
Check if the exact displayed times fit a strict subtraction:
From 6:38 AM to 6:38 PM is 12 hours.
From 6:38 PM to 6:53 PM is 15 minutes.
Total straight subtraction of displayed numbers = 12h 15m.
Because 12h 14m appears on screen while the raw math says 15m, the app is almost certainly calculating daylight using exact internal timestamps (including seconds/refraction corrections) and then displaying human-readable rounded time labels separately that do
* * *
Copilot:
Why does my weather app tell me today has 12 hours and 14 minutes of daylight, when by my calculation, it has 12 hours and 15?
Your weather app isn’t wrong — it’s just using more precise astronomical rules than the simple “sunset minus sunrise” subtraction you’re doing.
Here’s the real reason you’re seeing 12h 14m instead of 12h 15m, and it’s surprisingly subtle.
🌞 1. Your calculation assumes sunrise/sunset are exact instants
You’re doing:
Sunset time – Sunrise time = Day length
But sunrise and sunset times published in apps are rounded to the nearest minute.
If the true times are:
Sunrise: 6:38:29
Sunset: 18:52:43
Your subtraction gives:
12 hours, 14 minutes, 14 seconds
But your human calculation rounds both to the nearest minute:
Sunrise: 6:38
Sunset: 18:53
Difference: 12h 15m
So your number is off by ~45 seconds simply because you’re subtracting rounded values.
Your app uses second‑level precision, even though it only displays minutes.
🌅 2. Weather apps use the “center of the Sun” definition
Astronomically:
Sunrise = moment the upper limb of the Sun appears
Solar day length = time between when the center of the Sun crosses the horizon
Those two definitions differ by 30–50 seconds depending on your latitude.
Your app uses the center‑of‑disk definition internally.
Your manual subtraction uses the upper‑limb definition.
That alone can shift the day length by up to a minute.
🌫️ 3. Atmospheric refraction adds another 30–90 seconds
The atmosphere bends sunlight upward, making the Sun appear earlier and disappear later.
But refraction varies with:
temperature
pressure
humidity
Apps use a standard refraction model, not the exact conditions at your location.
This introduces another small offset — often 20–40 seconds.
🧭 4. Longitude rounding inside the time zone
Saint‑Jean‑sur‑Richelieu is east of the Eastern Time zone’s reference meridian.
That means your solar day is naturally a few minutes earlier than the “ideal” ET location.
Apps correct for this precisely.
Your manual subtraction does not.
✔️ The bottom line
Your weather app is using:
exact astronomical definitions
second‑level precision
atmospheric refraction models
your exact latitude/longitude
You’re subtracting two rounded clock times, which introduces a ~45–75 second error.
That’s why the app says 12h 14m, while your subtraction gives 12h 15m.
If you want, I can compute your exact solar day length today down to the second using your latitude in Saint‑Jean‑sur‑Richelieu.
* * *
Copilot:
Why do people complain that Daylight Savings Time forces children to get up in the dark; I would have thought the contrary...
The short answer: people complain about kids waking up in the dark because of permanent Daylight Saving Time (DST), not because of switching back to Standard Time.
And the reason is surprisingly simple once you look at the clock math.
🌅 The key idea
DST shifts the clock one hour later relative to the sun.
So in winter—when sunrise is already late—DST pushes sunrise even later.
Example: Montreal / St‑Jean‑sur‑Richelieu in December
Standard Time sunrise: ~7:3
DST sunrise: ~8:30
If school starts at 8:00, then:
On Standard Time, kids wake up around 6:30–7:00 → still dark, but dawn is approaching.
On DST, kids wake up around 6:30–7:00 → pitch black, and it stays pitch black until after they’re already in class.
That’s why people say DST forces kids to get up in the dark.
🌞 Why you might have thought the opposite
You’re probably thinking of summer, when DST gives long bright evenings and early sunrises.
But the complaints are about winter, when DST becomes a problem.
In summer:
DST = sunrise at 5:00 instead of 4:00 → still bright early
Kids wake up with plenty of daylight
No one complains
In winter:
DST = sunrise at 8:30 instead of 7:30 → extremely late
Kids walk to school in full night
Parents, sleep researchers, and safety experts complain loudly
🧠 The deeper reason: human biology
Our circadian rhythm is anchored to morning light, not evening light.
Permanent DST means:
Less morning light → harder waking
More evening light → later bedtimes
Chronic sleep debt, especially for teens
More accidents during dark morning commutes
This is why sleep scientists overwhelmingly support permanent Standard Time, even though it feels gloomier.
🧩 Why the confusion exists
Because DST feels like “more light,” people assume it helps mornings.
But DST actually steals morning light and gives it to the evening.
In winter, that trade‑off becomes brutal.
If you want, I can show you exactly how sunrise times shift for your latitude in Québec under both systems across the whole year—it’s very revealing.
So the high noon standard switches as well on Daylight Savings?
Yes — “high noon” shifts on the clock when you switch to Daylight Saving Time.
This is the part most people don’t consciously think about, but it’s the whole reason DST creates those dark winter mornings.
Let me break it down clearly and intuitively.
🌞 What “high noon” actually means
Astronomical solar noon = the moment the sun is highest in the sky.
On Standard Time, the clock is roughly aligned with the sun:
Solar noon happens around 12:00 (give or take depending on longitude).
On Daylight Saving Time, the clock is pushed one hour ahead:
Solar noon now happens around 13:00 (1 PM).
So yes — DST makes “noon” happen one hour later on the clock.
🕰️ Why this matters for morning darkness
If solar noon shifts one hour later, sunrise also shifts one hour later.
Example at your latitude (Montreal / St‑Jean‑sur‑Richelieu):
December
Standard Time sunrise: ~7:30
DST sunrise: ~8:30
Because DST pushes the whole solar day one hour later.
This is why kids end up waking up in pitch darkness under permanent DST.
🌅 A simple way to visualize it
Think of DST as taking the whole sky and sliding it one hour later on your clock.
🌍 Why your intuition might say “but DST gives more light!”
Because in summer, sunrise is extremely early:
Standard Time sunrise: ~4:50
DST sunrise: ~5:50
Still bright early, so no one notices the shift.
But in winter, sunrise is already late:
Standard Time: ~7:30
DST: ~8:30
That’s when the shift becomes painful.
🧠 The bottom line
Yes — DST moves high noon to 1 PM, and that’s exactly why winter mornings become so dark under DST.
People complain because the clock is no longer aligned with the sun, and biology cares deeply about morning light.
If you want, I can show you a full year graph of sunrise/noon/sunset at your latitude under both systems — it makes the difference jump off the page.
* * *
Gemini:
At what time will the Fall Equinox 2026 happen in Greenwich, England?
The Fall (Autumnal) Equinox in 2026 occurs on Wednesday, September 23, 2026, at 00:05 UTC [cite: 1.1.1].
Local time in Greenwich, England depends on whether you mean standard time or local clock time observing British Summer Time (BST):
Greenwich Mean Time (GMT / UTC): 00:05 GMT on September 23, 2026 [cite: 1.1.1]
Local Clock Time (BST, UTC+1): 01:05 BST on September 23, 2026 (some observatory/ephemeris tables list local equinox calculations right around 01:05–01:06 BST)
At what time will the Fall Equinox 2026 happen in Greemwich, England happen?
The Fall (Autumnal) Equinox in 2026 occurs on Wednesday, September 23, 2026, at 00:05 UTC [cite: 1.1.1].
Local time in Greenwich, England depends on whether you mean standard time or local clock time observing British Summer Time (BST):
Greenwich Mean Time (GMT / UTC): 00:05 GMT on September 23, 2026 [cite: 1.1.1]
Local Clock Time (BST, UTC+1): 01:05 BST on September 23, 2026 (some observatory/ephemeris tables list local equinox calculations right around 01:05–01:06 BST)
* * *
No comments:
Post a Comment