A study from Colorado University suggests deja vu might occur when someone is in a situation that is similar to a previous experience of theirs, and although they feel the familiarity of the situation, they are unable to recall the previous experience (so they have a feeling of familiarity that is without an apparent cause.)
So when I’m in deja vu and the “familiarity” feels days or weeks (or months) old—which is basically every experience of mine—it might be because the memory causing the feeling is that old! I just can’t quite recall that previous memory.
And yes, I experience deja vu, most recently yesterday when I was talking to someone. It was distracting!