You should read the disclaimer which can be found in the Help Topics file prior to using Dark Skies?
The help file exists to enable you to familiarize yourself with the program's features?
That you can toggle the daylight savings time option on and off?
Astronomical twilight is defined to end when the sun is past 18 below the horizon?  It is the time when reliable astronomical measurements can be started.
Nautical twilight starts when the sun is 6 below the horizon and ends when the sun is 12 below the horizon.  At its beginning you can make out the first few bright stars and when it ends you can make out most of the stars in the sky.
Civil twilight starts at sunset and ends when the sun is past 6 below the horizon.  It is the time when you can perform outdoor activities and still see fairly well.
You can toggle the grid lines on and off?
That the moon can interfere with dark viewing even before it rises? This is because it shines onto the top of the atmosphere, and brightens it before you can even see the moon.
You can display the dark sky calendar for the whole year, for a single month or for a single day?
You can toggle the time of full and new moons display on and off?
The exact time for the full moon is not necessarily during the night time for your location?  This is because the rotation of the earth on its axis  and the rotation of the moon in its orbit are independent.
This is the last tip : you can turn of your tip of the day now.