(Disclaimer: following is my merely my own opinion and experience)
Day birth or night birth? Under certain circumstances this can be a difficult question for many practitioners. A lot of often complicated measures have been devised to deal with the diffiulties of twilight births (and events too) I'm afraid I have a simple mind, so what I've always done in these questions is as follows:
-what was the exact time of the birth (or event-or horary question)
-then I look up that time on a sunrise/sunset calendar (for the date and place)
-if the time is after the given sunrise time, to me its "day"; if it is before the given sunset time, its "day"
-if the time is before the given sunrise time, its "night"; if after the given sunset time, its "night
HOWEVER
There is one additional factor. I believe (for astrological calculations) in the "real" time (sun time-aka sundial time, which was universally used in astrology prior to the invention of civil-local mean time-in the 1800's)
The official clock time given everywhere is local mean time-but we want to know if in fact the body of the sun has cracked the horizon, or is beneath it. There is a varying difference between civil clock time and the sun's time-from as little as 1 minute difference (fast or slow relative to the clock), to as much as 15 minutes on some days of the year. Since what I want to know, in the question here, is whether the sun is ACTUALLY above (or below) the horizon, I google "Daily Sun Data", then check the date, and find if the sun is faster or slower than clock time. I then check the birth (or event) time against the civil sunset/sunrise time, then modify that using the "Local Apparent Time" given in the Daily Sun Data table. This tells me if the sun were actually up (day) or down (night) at the birth or event time.
Example:
Event occured (we'll say) at 6:45 pm (clock time) in Hollywood California on such and such date: was it a day event (sun not having yet set) or was it a night event (sun under horizon). I look up sunrise/sunset for the date and location: I find the sun set (civil clock time) at 6:40 pm; but I now look at the Daily Sun Data table and find that the sun's time on that day is 12 minutes slower than clock time: this means that the sun actually went below the horizon that day 12 minutes later than the given clock time: ie, in this example actual sunset occured at 6:52 pm (not 6:40 pm) Since our event occured at 6:45 pm (clock time), and since the sun actually did not go below the horizon until 6:52 pm, our event turns out to actually be a day (sun still above the horizon) event.
Anyway, that's how my simple mind handles the question of day or night, and also the determination of planetary hours. Has worked well for me over the years, thought I'd pass it along (for what its worth)