CreatureOfPrometheus t1_j7b1kpc wrote
The variation in day length is caused by Earth-Sun geometry, so any change from 1700 to now is negligible.
I can think of two factors that might contribute:
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Was there summer time/winter time in that locale in 1718? If not, then "10pm dark" then should be like "11pm dark" now.
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In 1718, there were probably no time zones, so 12pm was measured from local solar noon. Depending on where you are in your timezone, there could be a shift of clock noon from solar noon. It's usually mild (should be <30 min), but is worse in some places due to political boundaries. It would shift both summer and winter sunset times the same, though.
AUniquePerspective t1_j7ccxje wrote
I don't know if it is the same for cities in Rheinland-Pfalz but I believe Berlin abandoned Local Mean Time in 1893 in favor of CET (Central European Time UTC +1). Currently Rheinland-Pfalz uses CET in winter and CEST (Central European Summer Time UTC +2) in summer.
LMT Local mean time differs from apparent solar time as can be observed with a sundial in that time is constant with LMT but the speed of time varies with a sundial.
This is all confusing without examples so...
At Mainz on this year's summer solstice, the sun will rise at 5:17 CEST, reach solar noon at 13:28, and set at 21:39 CEST.
And on this year's winter solstice, the sun will rise at 8:22 CET, reach solar noon at 12:25, and set at 16:27 CET.
There are (by subtraction) 8 hours ten minutes between noon and sunset midsummer and 4 hours between noon and sunset midwinter. This explains the timing of the candle law.
Edit: But it's also important to recall that sunset isn't the time it gets too dark. There are 3 phases of twilight. During Civil Twilight it is generally possible to do outdoor activities though the sun is below the horizon. During nautical twilight, if the sky is clear, the brighter stars are visible and so is the horizon. During astronomical twilight, some stars that would otherwise be visible are obscured by sunlight.
yanessa t1_j7cdk0u wrote
ad1) summer/winter time was introduced in the 20th century (first official use 1908 inOntario, Canada) so n.a. here
ad2) time zones started being used in the latter 19th century for railways
the differing hour length from medieval time measurement is a better bet
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