In addition to the 'Now' button, another program I use, that will remain unnamed, also has  'Sunrise' & 'Sunset' buttons that I use quite often. On most evenings I'll click 'Sunset' then use their keyboard shortcuts to quickly advance the time to match the time I plan on observing.

Also, maybe add an 'Apply & Close' button so the new time is applied then the popup is closed. I think reducing keystrokes is always a good thing, especially if you are using AP outside, in the dark.