You Are Remembering It Wrongly
We think we can remember things, sometimes from long ago, and often vividly. While that seems to be the case, and the memories are precise and clear, they are often wrong, sometimes utterly so.
The process of recollection is not like retrieving a file, however old it may be, and reading its unchanged contents. Rather, it is like watching and hearing yourself tell the story again, and in each telling there are minor changes, sometimes two stories getting mixed up, and with interruptions and other people's comments mixed in.
In that sense our memories are remade over time. And while seemingly clear and accurate they cannot be relied upon.