If you can around your work schedule, you could try adjusting your schedule a little bit later over the next couple days, so that you're waking up 3 or 4 hours later and therefore staying awake 3 or 4 hours later. But, I'd do that ASAP – like, tonight stay up till 1 am, so that you're more adjusted to it by Wed. Do that only if you've previously been able to stay up late and sleep later and feel OK, though – 3 days isn't long enough to find out it doesn't work and go back to your prior method.
On the day of the exam, call the testing center earlier and see if it would be OK if you came in a few hours early. For my last exam (REG), 6pm was the only available time slot on the day that I was going to take it, so I scheduled for 6pm, but I also went to bed around 9 and had a 1.5 hour drive back after the test, so didn't like the 6pm slot at all. I called the test center around 10 or 11 the day of the test and asked if it would be OK for me to come in earlier – like 1 or something like that – and they said that'd be fine, they had open computers that day. So, if your test center is similar, you might be able to test early even though your appointment is late.
On the flip-side of things, I ended up not getting to the test center till nearly 6:30 due to car troubles (with 2 different vehicles – long story, but in summary, started the trip with 1 car planning to test around 1 or 2, turned back, switched cars, had trouble with the second one too, and finally made it to the test center at 6:27 or so after car repairs 😐 ). So, I ended up taking the exam even later than 6, and still ended up passing it. For me, the adrenaline of test-taking (combined with the adrenaline of fighting car problems, but I think probably the test-taking alone would've been enough) kept me awake and alert through the exam. Driving back at and after bedtime was a little rough, but I made it. 😛 I did drink an energy drink as I neared the testing center, and maybe had another on a break, I don't remember (that was the only test I took a break on, just cause I was a ball of nerves after being within minutes or maybe just seconds of missing my test 😐 ).
So, I'd say call on the 31st and see if the testing center will let you start early. If so, awesome! If not, adrenaline – esp if aided by an energy drink – can do wonders to get you through it. I usually did the 1 or 1:30 test times, so wasn't looking forward to the 6 at all, but it ended up working out OK.
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