Depends. It was awhile ago, but I think they would have let me take one at another time but because the day I had 4 finals was actually the last day of finals the only other time available was obviously earlier. (Plus my school had a weird setup. First day of finals was a Wednesday and last day was Monday. No finals on Sunday, which meant an extra day or two available to study. I can't remember if they said the option was to take it Friday because the teacher wasn't available on Saturday or whatever.) So I said fuck that and just took them all that day (Monday).

I kind of regretted it when my brain was fried at the end of the day but what the hell. I more than passed. I think the extra day or two of studying (however long it was) helped.