Length of the Night

as an interval between the PM and AM moments of Sun passing a given angular height (default -6°, for the ``civil night''):

Year:   Month:   Day:
Longitude: (western as -)   Latitude:
Your Time - UTC:  h
The relevant angular height of Sun is degrees
next days will be computed as well,
with a step of day(s).
   save settings    use my saved settings

Another option is to use your own command line (ev. overriding all previous data):

(`?' gives help). 

The centre of Sun is at a place with coordinates [Lambda=16.6°, Phi=49.2°]
 in an angular height of h =-6.0°
 in the following morning and evening moments (given in UTC+ 1h):

 year-month-day  morning evening twilight decl.  >mean  night   A-W
                       h:min     / 1 min   /1°   /1min   /1h    /1°
2025- 2-17 Monday   6:26  17:49   32.9  -11.81   -14.0  12.60  -11.1
        18 Tuesday  6:24  17:51   32.8  -11.46   -13.9  12.55  -10.6
        19 Wednesd  6:22  17:53   32.7  -11.10   -13.8  12.49  -10.1

Average for   3 days
from   3 values is  6:24  17:51   32.8  -11.46   -13.9  12.55  -10.6

Meaning of remaining columns:
 Twilight    is an interval to/from h=-0.8°
 Declination of Sun is given for the moment of local mean noon,
 >Mean       says how much is the Sun ahead of the mean time,
 Night       is the time the Sun travels below h,
 A-W         is departure of solar azimuth from the west when at h afternoon.

This is a result of the programme nights (available as a part of a package pas_jh.zip (1.2 MB) -- the needed Pascal units themselves are unzipped within this directory, the whole tree of my programmes within this directory) with a command line: 
nights  d17.02.2025 t23:58 l16.6 f49.2 ut1  h-6 n2 i1