Why are banks allowed to arbitrarily reorder and re-post the time and day of account debits?

If you bank online you may have noticed the algorithmic activity that reorders and re-posts the dates and times of debits, checks, fees anything and for the purpose of maximum payout of overdraft fees should the account go into the red. Apparently a lot of banks are doing this. This has to be illegal - it is clearly wrong - and wreaks havoc for anyone trying to keep accurate daily accounting. I've had a single check switch days it was posted by as much as 4 days - it "posted" one day, was gone and then reappeared 4 days later. Checking the account activity 1 or more times a days demonstrates these manipulations. To note - the people who are most hurt by this are the poor who use checking - this has to be stopped.