I'm on U.S. Central Time (CST), and know that some people trade after ARCA opens at 4:00am CST. However, I've noticed trades going through at 10pm or 1am on NASDAQ and AMEX stocks. HOW is someone able to trade at those hours when I cannot? WHO is making these trades late at nite or early morning before ARCA opens? These trades between 10pm and 1am at nite are often large blocks or consistent blocks of 100 every few seconds, and do not show up on ARCA, only showing on Time and Sales. WHY do these late traders trade in large blocks(such as 300,000 shares) or consistent trades of 100 shares? WHAT is the purpose?