A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Date: 2016 Sep 26, 22:28 -0700
The apparent diameter of the sun has nothing to do with it. As it only varies by 3.3 % throughout the year, it could not have that big an effect. But it will create some noise on top of the actual cause. Here is a hint: Why does nautical twilight on the equator last 2min 15sec longer at solstices than at the equinoxes? For the same reason.
If you are skeptical, check the almanac or with an astrologer.