Yes, the inservice exam is held around October. It is program-dependent whether it's required for you to take it. My program offered it to most interns as an optional self-evaluation, but it was required for second years and for interns who are fast tracking.
If you have to take it as an intern, keep in mind that your score is only compared to that of other interns across the country -- they do not include the 2nd and 3rd years in the calculation of your score.