A calendar can keep the date while losing the reason it mattered.

Repeating entries outlive their origins. A date keeps arriving each year long after the arrangement that created it has ended, and it can take a while to remember why it is there at all. Sometimes the answer is trivial, and sometimes the date is holding something you have not thought about in a long time.

When a recurring entry appears and you cannot place it, spend a moment on where it came from before deleting it. If it turns out to matter, you might write the reason beside it so that a future version of you is not left guessing.