Let me point out a couple of flaws in your argument here. First, by the age of 20 (that's my age just for your reference) most average teenagers have had several jobs for, many of which will have been 9 to 5, 5 days a week jobs. They (and I too) know the daily grind.
Which brings me to my next point. How much you love your job does affect how you see time passing. My best example is a camp counciling job I took for a few summers. I was on the job everyday, from the moment I got out of bed to the minute my head hit the pillow. I had to take care of a whole gaggle of the rowdiest and most chaotic kids you've ever seen, with my only sweet respite was when I went to sleep, and sometimes not even then. And yet, the entire month shift I was there per year flew by, because I loved that job so much. There was never a moment when I prayed for sleep, because there were always things I was doing that filled that time.
Also who just surfs the internet when they're bored? you can potentially read every book you've ever loved there, see whole tv series' in a row, and play enough games to drown the most avid gamer (aka me). I myself once started watching How I Met Your Mother, and suddenly my alarm went off, signaling that I had to head off to watch Iron Man 2, a movie I had been waiting to see for months. The time that had passed between the moment I started watching and the alarm? 5 hours. Over half of a day shift disappeared and I didn't even notice.
So yeah, if you really can't find something to do that you enjoy in order to kill time, you're honestly not trying.
Off Topic: Seriously, Hawaiian Shirt Friday? Who the heck does that anymore?