[walrus01]

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.

[AStonesThrow]

> sunrise and sunset, which is obviously solar

Is it now?

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.

[walrus01]

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.

https://www.astropixels.com/ephemeris/soleq2001.html

[AStonesThrow]

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?

[walrus01]

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.

[AStonesThrow]

> dependent on the sun's position

Check your geocentrism

The Sun’s relative, apparent position.

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?