Applies to both sides.
"The accuracy decreases linearly (2% per tile or 0.125% per voxel) when shooting beyond the limit of the firing mode: auto shot: 7 tiles or 112 voxels, snap shot: 15 tiles or 240 voxels, aimed shot: no penalty"
It's the same range penalty in day or night. Could be an interesting mod to make the long range penalty even bigger at night... Another interesting mod would be that the accuracy is shown on your cursor, so you actually see what the real accuracy after the calculation is.