forum "last post" information is unreliable?

Hi,

I noticed this:

“6 years ago” would be 2019. That post is 2021. how is that possible that he wasnot seen for 6 years while posting 4 years ago?

Is that information even reliable or just a fantasy thing?

That's because, when he posted in Sep 2021, his last post was from 6 years ago - 2015.

Oh thank you. I didn’t even think it could mean that.