In fact, it is more or less the same prime time, with a few differences. Lots of people log on after work, if only to collect the day's e-mail. The evening hours are prime time for surfing and downloading.
Weekends are popular, too, though more in the late evening than in the daytime.
Of course, you have to take time differences into consideration. On top of all this, more people are logging on throughout the day from work. For now, a recognizable crowding occurs on the U.S. servers during the evenings. Sunday evenings and late Fridays are especially jammed. If you're on the Web a lot, you notice the slower response times during those periods.