<p>The test designers try to eliminate fluctuations in difficulty by modifying the curves appropriately. This is the purpose of giving scores from 1-36 instead of just the number of questions you got right--to take into account that one test might be slightly more or less difficult than another.</p>
<p>OP: ACT curves are set beforehand so the test date is largely irrelevant in determining the overall performance of people taking the test.</p>