[Previously: part I Geolocator.]
A new feature for my d3-celestial star map: A sky color gradient that shows the current sky state at the set time and date if the projection is hemispheric. No extra coding needed, just set daylight.show to true in the configuration of check "Daylight Sky" in the form. Time zone still needs to be set manually and horizontal refraction isn't considered yet, so the result need not be entirely accurate.
[Next: part III Geolocator: Markers.]