You compared knowing the date of creation to the date of an imaginary apostasy. That is analogy. Had you used "like" or "as" then it would have been a simile.
It wasn’t a comparison. It was a lesson in reasoning (you failed by the way). You said if a person couldn’t date an event (like the apostasy of your church) then it didn’t happen. I tried to show you through logic that some dates cannot be known exactly because they were lost to time. We cannot date Creation but we know it happened from the fact we are here now. To say it didn’t happen because we cannot pinpoint the exact date in time is ridiculous as is your argument.