After Hours S&P 500
The futures market trades 24 hours a day, 5.5 days a week. S&P 500 futures market continues trading, and this gives pricing exposure and influences the individual stocks when they resume trading in US session. "My original answer contained a fundamental error: it turns out that it is not true that any exchange can create its own product to track any underlying index.  If the underlying index is copyrighted (such as the S&P indices, Russell indices, Dow Jones indices, etc.) then the exchange must enter into a licensing agreement (usually exclusive) with the copyright holder in order to use the index's formula (and name).  Without such a license the exchange would only be able to approximate the underlying index, and I don't think that happens very much (because how would you market such a product?). The CME offers several futures (and other derivatives) whose face value is equivalent to some multiple of the S&P500's value on the date when the product expires.  When such a product is actively traded, it may serve as a reasonable indicator of the ""market""'s expectation of the S&P500's future value. So, you could pay attention to the front month of the CME's S&P 500 Mini future, which trades from 17:00-16:00 Chicago time, Sunday night through Friday afternoon.  But remember that the prices quoted there are As another example, if you care about the Russell 2000 index, until 2017 the ICE Exchange happened to hold the license for its derivatives.  They traded from 20:00-17:30 New York time, Sunday night through Friday afternoon.  But in mid-2017 CME bought that license as well, so now you'll want to track it here. Moral: There's almost always some ""after hours"" product out there tracking whatever index you care about, but you may have to do some digging to find it, and it might not be all that useful for your specific purpose."
Well i dont know of any calculator but you can do the following 1) Google S&P 500 chart 2) Find out whats the S&P index points (P1) on the first date 3) Find out whats the S&P index points (P2) on the second date 4) P1 - P2 = result "The ex indicator is meant to be a help for market participants.  On the ex-day orders will go into a different order book, the ex order book, which at the start of the ex day will be totally empty, i.e. no orders from the non-ex day book have been copied over. Why does this help?  Well imagine you had a long-standing buy order in the book, well below the current price, and now the share price halves due to a 2-for-1 split, would you want to see your order executed? If so, your order should have gone into the ex-book which is only active on the ex-day (and orders in the ex book are usually copied over to the normal book on the day after the ex-day but this is exchange-specific). Think of it as an additional safety net to tell the exchange: ""I know what I'm doing: I want to buy this stock totally overpriced after the 2-for-1 split"". Now some exchanges and/or some securities (mostly derivatives) linked with the security in question don't have this notion of ex or the ex-book, and they will tell you by ""will not be quoted ex"" or ""the ex indicator is missing"". In your case (SNE) it is a sponsored ADR, the ex-date was Mar 28 2016, one day before the ex date of the Japanese original.  According to my understanding of NYSE rules, there is no specific rule for or against omitting the ex-indicator.  It seems to be a decision on a case by case basis.  Looking through the dividends of other Japanese ADRs I drew the conclusion none of them have an ex-book and so all of them are announced as: ""Will not be quoted ex by the exchange"".  Again, this is based on my observations." "The gap up/down and rapid movement immediately following market open is due to overnight futures activity. In your example, SP500 on June 20, 2016 saw a 20-point gap up at market open. This was because the SP500 futures were trading 20 points higher at 9:30 AM than at its close on Friday. The index will always ""catch up"" with futures at market open. You can see that below. The top chart is the E-mini SP500 futures from Sunday night to Monday. Beneath it is the SP500 index." "A huge amount of money in all financial markets is from institutional investors, such as mutual funds, government pension plans, sovereign wealth funds, etc.  For various reasons these funds do all of their trading at the end of the day.  They care primarily that their end-of-day balances are in line with their targets and are easy to audit and far less about ""timing the market"" for the best possible trades. So, if you're looking at a stock that is owned by many institutional investors -- such as a stock (like AAPL) that makes up a significant portion of an index that many funds track -- there will be a huge amount of activity at this time relative to stocks that are less popular among institutions. Even just in its introduction this paper (PDF) gives a fair overview of other reasons why there's a lot of trading at end-of-day in general. (In fact, because of all this closing activity and the reliance on end-of-day prices as signposts for financial calculations, the end-of-day has for decades been the single most fraud-ridden time of the trading day.  Electronic trading has done away with a lot of the straight-up thievery that floor traders and brokers used to get away with at the expense of the public, but it still exists.  See, for example, any explanation of the term banging the close, or the penalties against 6 banks just last month for manipulating the FX market at the close.)" "The graphing tools within Yahoo offer a decent level of adjustment. You can easily choose start and end years, and 2 or more symbols to compare.  I caution you. From Jan 1980 through Dec 2011, the S&P would have grown $1 to $29.02, (See Moneychimp) but, the index went up from 107.94 to 1257.60, growing a dollar to only $11.65. The index, and therefore the charts, do not include dividends. So long term analysis will yield false results if this isn't accounted for.  EDIT  - From the type of question this is, I'd suggest you might be interested in a book titled ""Stock Market Logic."" If memory serves me, it offered up patterns like you suggest, seasonal, relations to Presidential cycle, etc. I don't judge these approaches, I just recall this book exists from seeing it about 20 years back." "NASDAQ has Pre and After market : NASDAQ Trading Schedule Regular Trading Session Schedule The NASDAQ   Stock Market Trading Sessions (Eastern Time) Pre-Market Trading Hours from 4:00 a.m. to 9:30 a.m.   Market Hours from 9:30 a.m. to 4:00 p.m.   After-Market Hours from 4:00 p.m. to 8:00 p.m.   Quote and order-entry from 4:00 a.m. to 8:00 p.m.   Quotes are open and firm from 4:00 a.m. to 8:00 p.m. You can trade in Pre/After Market but liquidity is very low. If an ""unexpected world events"" occurs, the volume/liquidity will most certainly increase. Another example is the Forex Market that's open 24/7 around the world. As one major forex market closes, another one opens. According to GMT,   for instance, forex trading hours move around the world like this:   available in New York between 01:00 pm – 10:00 pm GMT; at 10:00 pm GMT   Sydney comes online; Tokyo opens at 00:00 am and closes at 9:00 am   GMT; and to complete the loop, London opens at 8:00 am and closes at   05:00 pm GMT. This enables traders and brokers worldwide, together   with the participation of the central banks from all continents, to   trade online 24 hours a day. src" Like others have said, mutual funds don't have an intraday NAV, but their ETF equivalents do. Use something like Yahoo Finance and search for the ETF.IV. For example VOO.IV. This will give you not the ETF price (which may be at a premium or discount), but the value of the underlying securities updated every 15 seconds. "EDIT: It was System Disruption or Malfunctions August 24, 2015 2:12 PM EDT   Pursuant to Rule 11890(b) NASDAQ, on its own motion, in conjunction   with BATS, and FINRA has determined to cancel all trades in security   Blackrock Capital Investment. (Nasdaq: BKCC) at or below $5.86 that   were executed in NASDAQ between 09:38:00 and 09:46:00 ET. This   decision cannot be appealed. NASDAQ will be canceling trades on the   participants behalf. A person on Reddit claimed that he was the buyer. He used Robinhood, a $0 commission broker and start-up.  The canceled trades are reflected on CTA/UTP and the current charts will differ from the one posted below.  It is an undesired effect of the 5-minute Trading Halt.  It is not ""within 1 hour of opening, BKCC traded between $0.97 and $9.5"".  Those trades only occurred for a few seconds on two occasions.  One possible reason is that when the trading halt ended, there was a lot of Market Order to sell accumulated.  Refer to the following chart, where each candle represents a 10 second period. As you can see, the low prices did not ""sustain"" for hours.   And the published halts." Trading volumes are higher at the end of the day as many traders close their open positions. In the morning however, traders incorporate various factors like performance of worldwide markets overnight, any corporate or government announcements, global macro events, etc. With the S&amp;P 500's cyclically adjusted price to earnings ratio above 26 and inching closer to 30 everyday I would be inclined to disagree. Also price trends and technical indicators say nothing about over and undervaluation. If fact technical indicators are worthless in the real world. This doesn't really make sense, as the small cap indices have a similar rate of growth as the s&amp;p 500. The global scale has some relevance, but exports are included in GDP as well, so it's not the full story.  A better answer, as is noted in comments lower down, is that the S&amp;P does not **grow** at 6%. It *returns* 6% per year. The dividend yield of the s&amp;p is a bit over 2%. Dividends are not growth, they are simply income; they may also grow themselves, but rarely by 6% per year (in real terms). Additional income that's not paid out in dividends probably amounts to another 1-2%. Growth is the final 1-3%, which makes it roughly match GDP. The Dow is the top 30 companies in the USA representing different business sectors. Companies are replaced from time to time but a math equation keeps it statistically correct.   The S&amp;P 500 is the same concept as the Dow but with a much larger base of companies. There are lots of good answers on here already.  There are actually lots of answers for this question.  Lots.  I have years of experience on the exchange feed side and there are hundreds and thousands of variables.   All of these variables are funneled into systems owned by large financial institutions (I used to manage these - and only a few companies in the world do this so not hard to guess who I work for).  Their computers then make trades based on all of these variables and equations.  There are variables as whacky as how many times was a company mentioned in an aggregate news feed down to your basic company financials.  But if there is a way to measure a company (or to just guess) there is an equation for it plugged into a super computer at a big bank. Now there are two important factors on why you see this mad dash in the morning: Now most of the rest of the day is also automated trades but by the time you are an hour into market open the computers for the most part have fulfilled their calendar buys.  Everyone else's answer is right too.  There is futures contracts that change, global exchange info changes, options expiring, basic news, whatever but all of these are amplified by the calendar day changing. SeekingAlpha has a section dedicated to Short ETFs as well as others. In there you will find SH, and SDS.  Both of which are inverse to the S&P 500.  Edit: I linked to charts that compare SH and SDS to SPY. Do a share split.  Your initial 1 share each becomes 10 (or 100) shares each,  then you can sell/gift/etc shares as needed.