The cycle is pretty consistent year to year but there are some long term cycles. These cycles take thousands of years, however, so probably not much difference from 1718 to here. One is that the tile of the earth relative to its orbit varies between 22.1% and 24.5% in a cycle of 41,000 years. It currently is about in the middle at 23.4% but is slowly decreasing. This would impact amount of daylight. Also, there is a cycle where the earths axis wobbles. And a cycle where the earth's orbit changes from almost round (where it is now) to slightly more elliptical. And a cycle where the closest approach to the sun (currently Jan 3) and farthest distance from the sun (about July 4) slowly change dates. All of these (and probably others) will impact daylight durations but probably not very much in a few hundred years.
bobjkelly t1_j7bkvwa wrote
Reply to Is the yearly cycle of varying daylight durations from day to day throughout time consistent? Is the cycle we have today the same as in the 17th century? by meellowstar
The cycle is pretty consistent year to year but there are some long term cycles. These cycles take thousands of years, however, so probably not much difference from 1718 to here. One is that the tile of the earth relative to its orbit varies between 22.1% and 24.5% in a cycle of 41,000 years. It currently is about in the middle at 23.4% but is slowly decreasing. This would impact amount of daylight. Also, there is a cycle where the earths axis wobbles. And a cycle where the earth's orbit changes from almost round (where it is now) to slightly more elliptical. And a cycle where the closest approach to the sun (currently Jan 3) and farthest distance from the sun (about July 4) slowly change dates. All of these (and probably others) will impact daylight durations but probably not very much in a few hundred years.