Market Hours and Valuations
"Company values (and thus stock prices) rely on a much larger time frame than ""a weekend"".  First, markets are not efficient enough to know what a companies sales were over the past 2-3 days (many companies do not even know that for several weeks).  They look at performance over quarters and years to determine the ""value"" of a company.  They also look forward, not backwards to determine value.  Prior performance only gives a hint of what future performance may be.  If a company shut its doors over a weekend and did no sales, it still would have value based on its future ability to earn profits." Stock values are generally reflective of a company's overall potential; and to some extent investor confidence in the prospect of a continued growth of that potential. Sales over such a short period of time such as a single weekend do not noticeably impact a stock's valuation.  A stock's value has more to do with whether or not they meet market expectations for sales over a certain period of time (generally 1 quarter of a year) than it does that they actually had sales (or profits) on any given day. Of course, catastrophic events, major announcements, or new product releases do sometimes cause significant changes in a stock's value.  For this reason you will often see stocks have significant volatility in periods around earnings announcements, merger rumors, or when anything unexpected happens in the world that might benefit or hurt their potential sales and growth. But overall a normal, average weekend of sales is already built into the price of a stock during normal trading.
The NYSE holidays are listed online here: https://www.nyse.com/markets/hours-calendars thanks.  I have real time quotes, but in the contest, if you put in a market order the trade might happen at the delayed quote price and not the real time price.  Does anyone know at which price it will trade, delayed or real time? The closest I can think of from the back of my head is http://finviz.com/map.ashx, which display a nice map and allows for different intervals. It has different scopes (S&P500, ETFs, World), but does not allow for specific date ranges, though. Hours appear to be relatively consistent, at least in my experience.  Analysts (all levels) have much more flexible schedules and travel much more but are responsible for more information/responsibility.  The difference is that associates do the grunt work with models/writing and analysts provide more direction/fine tuning and interact with clients more(they're on the phone half the time from 7-4 every day). Its generally not night work but if a company announces earnings after market close and then has an evening conference call, we need to have the report out by the next morning well before the market opens, so yeah sometimes it can get pretty late. "During market hours, there are a lot of dealers offering to buy and sell all exchange traded stocks. Dealers don't actually care about the company's fundamentals and they set their prices purely based on order flow. If more people start to buy than sell, the dealer notices his inventory going down and starts upping the price (both his bid and ask). There are also traders who may not be ""dealers"", but are willing to sell if the price goes high enough or buy if the price goes low enough. This keeps the prices humming along smoothly. During normal trading hours, if you buy something and turn around and sell it two minutes later, you'll probably be losing a couple cents per share. Outside normal market hours, the dealers who continue to have a bid and ask listed know that they don't have access to good price information --  there isn't a liquid market of continuous buying and selling for the dealer to set prices he considers safe. So what does he do? He widens the spread. He doesn't know what the market will open tomorrow at and doesn't know if he'll be able to react quickly to news. So instead of bidding $34.48 and offering at $34.52, he'll move that out to $33 and $36. The dealer still makes money sometimes off this because maybe some trader realized that he has options expiring tomorrow, or a short position that he's going to get a margin call on, or some kind of event that pretty much forces him to trade. Or maybe he's just panicking and overreacting to some news. So why not trade after hours? Because there's no liquidity, and trading when there's no liquidity costs you a lot." The usual lazy recommendation: See what similar objects, in similar condition, of similar age, have sold for recently on eBay. That establishes a fair market value by directly polling the market. "Nobody has mentioned the futures market yet. Although the stock market closes at 4pm, the futures market continues trading 24 hours a day and 5.5 days a week. Amongst the products that trade in the future market are stock index futures.  That includes the Dow Jones, the S&P 500. These are weighted averages of stocks and their sectors. You would think that the price of the underlying stock dictates the price of the average, but in this day and age, the derivative actually changes the value of the underlying stock due to a very complex combination of hedging practices. (this isn't meant to be vague and mysterious, it is ""delta hedging"") So normal market fluctuations coupled with macroeconomic events affect the futures market, which can ripple down to individual stocks. Very popular stocks with large market caps will most certainly be affected by futures market trading. But it is also worth mentioning that futures can function completely independently of a ""spot"" price. This is where things start to get complicated and long winded. The futures market factor is worth mentioning because it extends even outside of the aftermarket and pre-market hours of stock trading." This question is impossible answer for all markets but there are 2 more possibilities in my experience: The opening price is derived from new information received. It reflects the current state of the market. Opening Price Deviation (from Investopedia): Investor expectation can be changed by corporate announcements or   other events that make the news. Corporations typically make   news-worthy announcements that may have an effect on the stock price   after the market closes. Large-scale natural disasters or man-made   disasters such as wars or terrorist attacks that take place in the   afterhours may have similar effects on stock prices. When this   happens, some investors may attempt to either buy or sell securities   during the afterhours. Not all orders are executed during after-hours trading. The lack of   liquidity and the resulting wide spreads make market orders   unattractive to traders in after-hours trading. This results in a   large amount of limit or stop orders being placed at a price that is   different from the prior day’s closing price. Consequently, when the   market opens the next day, a substantial disparity in supply and   demand causes the open to veer away from the prior day’s close in the   direction that corresponds to the effect of the announcement, news or   event. You typically need to specify that you want the GTC order to be working during the Extended hours session. I trade on TD Ameritrade's Thinkorswim platform, and you can select DAY, GTC, EXT or GTC_EXT. So in your case, you would select GTC_EXT. "One idea: If you came up with a model to calculate a ""fair price range"" for a stock, then any time the market price were to go below the range it could be a buy signal, and above the range it could be a sell signal. There are many ways to do stock valuation using fundamental analysis tools and ratios: dividend discount model, PEG, etc. See Wikipedia - Stock valuation. And while many of the inputs to such a ""fair price range"" calculation might only change once per quarter, market prices and peer/sector statistics move more frequently or at different times and could generate signals to buy/sell the stock even if its own inputs to the calculation remain static over the period. For multinationals that have a lot of assets and income denominated in other currencies, foreign exchange rates provide another set of interesting inputs. I also think it's important to recognize that with fundamental analysis, there will be extended periods when there are no buy signals for a stock, because the stocks of many popular, profitable companies never go ""on sale"", except perhaps during a panic. Moreover, during a bull market and especially during a bubble, there may be very few stocks worth buying. Fundamental analysis is designed to prevent one from overpaying for a stock, so even if there is interesting volume and price movement for the stock, there should still be no signal if that action happens well beyond the stock's fair price. (Otherwise, it isn't fundamental analysis — it's technical analysis.) Whereas technical analysis can, by definition, generate far more signals because it largely ignores the fundamentals, which can make even an overvalued stock's movement interesting enough to generate signals." After-hours trading and alternate venues allow one to trade outside of regular market hours. However there are a few reasons why you would not want to: The purpose of an exchange is to improve liquidity by gathering all buyers and sellers in the same place at the same time. If trading was 24/7, not all market participants would be trading at the same time. Some markets (including NASDAQ) depend on market makers or specialists to help liquidity. These exchanges are able to mandate that the market maker actively make a market in a security during a meaningful percentage of the trading day. Requiring 24/7 active market making may not be reasonable. Trading systems, meaning both exchange infrastructure and market participant infrastructure, need maintenance time. It's nice to have the evenings and weekends for scheduled work. Post-trade clearing and settlement procedures are still somewhat manual at times. You need staff around to handle these processes. "You'd have to check the rules for your broker to make sure that the term is being used in its usual sense, but the typical answer to your question is ""no.""  A GTC will execute during market hours.  You would need to explicitly specify extended hours if you want to execute outside of market hours (which your broker may or may not support)." I look at the following ratios and how these ratios developed over time, for instance how did valuation come down in a recession, what was the trough multiple during the Lehman crisis in 2008, how did a recession or good economy affect profitability of the company. Valuation metrics: Enterprise value / EBIT (EBIT = operating income) Enterprise value / sales (for fast growing companies as their operating profit is expected to be realized later in time) and P/E Profitability: Operating margin, which is EBIT / sales Cashflow / sales Business model stability and news flow "Using your example link, I found the corresponding chart for a stock that trades on London Stock Exchange: https://ca.finance.yahoo.com/echarts?s=RIO.L#symbol=RIO.L;range=1d As you can see there, the chart runs from ~8:00am to ~4:30pm, and as I write this post it is only 2:14pm Eastern Time.  So clearly this foreign chart is using a foreign time zone.  And as you can see from this Wikipedia page, those hours are exactly the London Stock Exchange's hours. Additionally, the closing price listed above the graph has a timestamp of ""11:35AM EST"", meaning that the rightmost timestamp in the graph (~4:30pm) is equal to 11:35AM EST.  16:30 - 11:30 = 5 hours = difference between London and New York at this time of year. So those are two data points showing that Yahoo uses the exchange's native time zone when displaying these charts."