you take it at the prometric exam center (location of your choice),
where they issue multiple exams so there are no set dates like the SAT.
first you have to apply for DENTPIN. it takes up to a week to get it. usually less.
you can register for the exam as early as next week once you get your DENTPIN.
you will get a calendar with all the available dates.
you can take it pretty much any day of the week,
depending on when the prometric center near you decides to open and close.