Besides different time zones, When, or what time of day do most people search on the internet. ie: North America is it during 1pm or 7pm? I just want to know when the busiest searching time is. title (know) sorry...lol
Are you talking general on the Internet, or on your own site? I'm usually only focusing on my own website and I use Google Analytics to track "everything", I can also see at what time most people arrive at my site from the search engines and what they have searched for. An interesting blog post on the topic is from problogger and is What Time Should You Publish Blog Posts.
I can not find the actual data for the global time spent over the net, You can search the internet user statistics and may know the how much time is spent on which areas over the net. I thinks 2pm to 5pm is the most busiest time on the net for the global users.
Not sure about the actual statistics for total volume, but each industry will be different. For some products, people primarily search for them while they are at work, others will mostly be at night, and some will be researched mostly on the weekend.