Financial settlement periods used to be much longer: Before the early 1990s at the London Stock Exchange, for example, stock could be paid for up to 10 working days after it was bought, allowing traders to buy (or sell) shares at the beginning of a settlement period only to sell (or buy) them before the end of the period hoping for a rise in price. This activity was identical to modern day trading, but for the longer duration of the settlement period. But today, to reduce market risk, the settlement period is typically two working days. Reducing the settlement period reduces the likelihood of default, but was impossible before the advent of electronic ownership transfer.
Aside from a risk/reward, the trader could also utilize other exit methods, such as waiting for the price to make a new low. With this method, an exit signal wasn't given until $216.46, when the price dropped below the prior pullback low. This method would have resulted in a profit of $23.76 per share. Thought of another way: a 12% profit in exchange for less than 3% risk. This swing trade took approximately two months.
The most significant benefit of day trading is that positions are not affected by the possibility of negative overnight news that has the potential to impact the price of securities materially. Such news includes vital economic and earnings reports, as well as broker upgrades and downgrades that occur either before the market opens or after the market closes.
ECNs and exchanges are usually known to traders by a three- or four-letter designators, which identify the ECN or exchange on Level II stock screens. The first of these was Instinet (or "inet"), which was founded in 1969 as a way for major institutions to bypass the increasingly cumbersome and expensive NYSE, and to allow them to trade during hours when the exchanges were closed.[6] Early ECNs such as Instinet were very unfriendly to small investors, because they tended to give large institutions better prices than were available to the public. This resulted in a fragmented and sometimes illiquid market.

This combination of factors has made day trading in stocks and stock derivatives (such as ETFs) possible. The low commission rates allow an individual or small firm to make a large number of trades during a single day. The liquidity and small spreads provided by ECNs allow an individual to make near-instantaneous trades and to get favorable pricing.
Many orders placed by investors and traders begin to execute as soon as the markets open in the morning, which contributes to price volatility. A seasoned player may be able to recognize patterns and pick appropriately to make profits. But for newbies, it may be better just to read the market without making any moves for the first 15 to 20 minutes. The middle hours are usually less volatile, and then movement begins to pick up again toward the closing bell. Though the rush hours offer opportunities, it’s safer for beginners to avoid them at first.