Gauge for Length of Day (showing Solstices & Equinoxes)


Happy Winter Solstice everyone!

Thanks to TWC’s seconds, my dials were more accurate this year than ever before…


When I examine the code, today’s day length was actually 6 seconds off from my actual location. I cannot blame my math… I cannot blame webCoRE… It is simply TWC reports the sunrise and sunset for a station a few miles away.

If anyone else wants to calibrate THEIR piston, I recommend running these two expressions today… right now… before midnight hits


Save the results to a text file, then later on, when you are bored, you can do the math to find the shortest day that TWC sees for your location.


Wow… Sometimes I am really impressed with my math…

Earlier this year, I estimated that using TWC for sunrise & sunset times will bring the results within 0.007% of accuracy…

The results for this year are in…

This Winter Solstice returned 0.042%… (instead of 0%)
(Which is exactly 6 seconds off, due to my location)
and of course…
0.007 x 6 = 0.042

The math could not be any more perfect!!
(not that anyone else cares, LOL)


First full day of Winter, and the new colors switched over on schedule…


The next six months, the dial will be moving towards the right…


… and so ends the three month period with the least amount of sunlight… (“Darkember”?)



We are exactly three weeks away from the Spring Equinox
(on the right gauge, it will be straight up at 50%)


For the observant folks, the right dial moves the fastest over the next six weeks…
(meaning the largest increases in daylight day-to-day)

Interesting side note:

As observed here, over the next six weeks the dayLightLength increases nearly the same number of seconds on a day-by-day basis. (the link above elaborates on this)

Analog vs Digital - Astronomical Observations

Ten days until the Equinox.


Notice how significant the right gauge moved in the past 11 days!!
(that much change could take 5-6 weeks near the Solstices)


The Equinox has come and passed, but I stalled a few days to be able to showcase this…

Here is 9 days straight… (4 days before and 4 days after the Equinox)

I still find it interesting how the “equal day & night” takes place a few days before the Equinox… not during, as we are taught growing up… (how many days depends on your latitude)

Also worth noting is how the dayLengthPercent crossed 50% about 1.1 days after the Equinox…

I should probably mention that even though the right gauge only displays hours & minutes, the math behind the scenes are actually measuring precise seconds, so this is what is actually happening in real life.
(IE: the day after the Equinox, the dayLength was dead center between the two Solstices)

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