In response to a forum post:Day and night change on map, and after considerable research, I created a map with a polygon overlay to show day and night:

It uses formulas from Solar Time | PVEducation to calculate the coordinates of the terminator (sunrise or sunset) based on day and time. It automatically adjusts for seasons and eccentricity, and is good through 2100. You can test it with manually entered dates and times, or set it to automatic (be sure to set your [Time Zone Offset] appropriately).

I thought it was a fun and interesting challenge. Lots of Trigonometry. Anyone find this interesting or useful?