Going south makes the earliest sunset happen later (because every sunset happens at the same time at the equator) and going west within a timezone makes it happen later too (since the sunset moves from east to west). Put those together and you get the diagonals.
The timezones are the thick grey lines on the map, and you can see they are causing breaks in the “rays”.
I’m not sure what’s causing the rays.
Going south makes the earliest sunset happen later (because every sunset happens at the same time at the equator) and going west within a timezone makes it happen later too (since the sunset moves from east to west). Put those together and you get the diagonals.