Check all SQL UPDATE queries that interact with that column in that table. Something, somewhere, is changing the format, and UPDATE is the only thing that I can think of that would do that.
EDIT: Re-read what you wrote. If you’re not doing ANY update queries… then… hmmm… is there any kind of automated/scheduled process that accesses that table?
Oh, got the culprit, there was one old script which had date inverse code which is the one who responsible for this.
any way, that is an stand alone script, how the heck itself auto executing ?