BioWare jettisoned the Day/Night cycle for Throne of Bhaal.
On their forums, back when BioWare had forums, they explained that the Day/Night cycle was more of a bother than a feature.
There was a frustration from fans about waiting around for shops to open and the implementation of clicking on a map traveling for 36 hours and showing up exhausted, without having rested, was pretty ridiculous.
In truth not having a Day/Night cycle is the choice that is consistent with the BG series as that's how BioWare evolved the gameplay for Throne of Bhaal.
I completely agree with this criticism. However, there are some better ways to implement day/night circles.