Sunset, also called sundown in some American English dialects, is the time at which the Sun disappears below the horizon in the west. It should not be confused with dusk, which is the point at which darkness falls, some time after the beginning of twilight when the Sun itself sets.

You can use this to figure out what time the sun will be setting.

This gives you the complete sun and moon data for the day.

According to "Guardian Unlimited"

The green ray is an optical phenomenon that occurs during the last moment of the sun's setting. Rarely seen from land, and then only when the horizon over the sea is 100% clear, it appears here, on a few pages of a flip-book which documents an entire sunset in Madagascar. The stills are taken from Tacita Dean's 2001 video Green Ray on Madagascar.

Double sunset 1999

Julie Delpy's waltz