Vítejte na GTA5-Mods.com

@Msanical You can make nights darker, but you'll have to change the timecycle files. I hope you have OpenIV installed.
Launch OpenIV / GTA V / mods/ common.rpf / data / timecycle. Extract all 'weather' XML files.
Then change the following figures. Copy the files back after you've changed them.
All files
<!-- Intensity of the upper surfaces lighting -->
<light_natural_amb_down_intensity> 0.0000 0.0200 --- --- --- --- --- --- --- --- --- 0.0200 0.0000</light_natural_amb_down_intensity>
<!-- Intensity of the lower surfaces lighting -->
<light_natural_amb_up_intensity> 0.0000 0.0200 --- --- --- --- --- --- --- --- --- 0.0200 0.0000</light_natural_amb_up_intensity>

All files but Thunder
<!-- Top of the sky -->
<sky_zenith_col_inten> 0.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0.0000</sky_zenith_col_inten>
<!-- Above the middle below the top -->
<sky_zenith_transition_col_inten> 0.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0.0000</sky_zenith_transition_col_inten>

All files
<!-- Sunrise is on the East-->
<sky_azimuth_east_col_inten> 0.0000 0.5000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0.5000 0.0000</sky_azimuth_east_col_inten>
<!-- North and South -->
<sky_azimuth_transition_col_inten> 0.0000 0.5000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0.5000 0.0000</sky_azimuth_transition_col_inten>
<!-- Sundown is on the west -->
<sky_azimuth_west_col_inten> 0.0000 0.5000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0.5000 0.0000</sky_azimuth_west_col_inten>

All files but Foggy
<fog_falloff> 1008.0000 --- --- --- --- --- --- --- --- --- --- --- 1008.0000</fog_falloff>

For Foggy only
<fog_falloff> 10.0000 0.5000 --- --- --- --- --- --- --- --- --- 0.5000 10.0000</fog_falloff>

All files but Thunder
<fog_base_height> -10.0000 --- --- --- --- --- --- --- --- --- --- --- -10.0000</fog_base_height>
<fog_haze_density> 0.0000 0.5000 1.0000 --- --- --- --- --- --- --- 1.0000 0.5000 0.0000</fog_haze_density>

All files (URBAN Only)
<sky_stars_iten> 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000</sky_stars_iten>