I often observe that the stock indices (Dow Jones, S&P etc) change in value even after the trading day has ended. Why does this happen? Is it because of adjustments that weren’t recorded previously.
In addition to William’s comments, specialists/market makers are sometimes working orders for closing prices, or working large orders up to the close. These executions are put through ‘as of’ the close of trading. The prices hit the tape, and can thus impact the index or indexes the stock is included in.
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