I was able to acquire some 10 mg tabs of generic valium, and over the course of a week took a few hundred milligrams. I had taken valium once before, but the dosage was too low for my body weight, so I never really felt much effect.
The first day I got the tabs, I took about 50 mg, and got a little drowzy and very relaxed. I did also smoke some pot, so it was tough to truly differentiate which effects were from what drug I took. Over the next few days, I took dosages ranging from 10 mg/day to 60 mg/day. By the end of the week I physically felt fine, but my ability to recall time, especially day of the week was strongly impaired. I recall being with some friends and having no recollection of what day of the week it was, I kept on thinking it was a Saturday, when in actuallity, it was Monday, and this happened for several days thereafter, even when I was I had not consumed any diazepam.
This inability to recall the day of the week lasted for 3-4 days and was very annoying. I am a student, so during this time I was studying/taking my exams (I never took the diazepam while taking any exams). I found that it did not, in fact, impair my ability to learn, and perform well on the exams; I actually did about the same as I always do. The only strange side-effect was this temporal distortion, which finally wore off.
Since I am a scientist, I plan on performming tests, on myself, and if I continue to have these strange side-effects, I will report them here.