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I compared 30 minute candles for AAPL in two platforms: TradingView and Thinkorswim. I was astonished of the discrepancy. The differences are HUGE! Here are screenshots as of Sep 25 2020.

TradingView:

Candlestick chart  in TradingView

Thinkorswim:

Candlestick chart in Thinkorswim

As you can see, the first 30 minutes candle is RED in Thinkorswim and it is GREEN at TradingView (the first candle 9:30 to 10:00 eastern).

Which one should I believe?

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  • 1
    Is your think or swim account just a papertrade account?
    – Hart CO
    Sep 25 '20 at 18:18
  • You should check if the bar intervals begin and end at the same time.
    – Flux
    Sep 25 '20 at 22:29
  • Candlesticks indicate an open and a close. Why would you want to know the "open" at some particular time such as say 11:30:00 ? (Note that "open" is in quotes, since, there is no open.)
    – Fattie
    Sep 26 '20 at 12:33
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The charts here are cropped so aggressively that they're difficult to compare systematically. It would be better to include the price axis labels. I think the grid is $1.00 for TradingView and $0.50 for Thinkorswim. In addition, the time axis labels should be clarified. I think the first TradingView candle outside the yellow-shaded (premarket) area is 9:30-10:00 ET; I think the Thinkorswim chart is labeled in CT so the corresponding candle is the "8:30" red one.

Given these interpretations, I find the TradingView chart more consistent with other sources, including what I see myself in Thinkorswim. The Thinkorswim chart shown here, which I am unable to replicate, shows a clear sign of inconsistency: The open of each candle is often far from the close of the previous (for TradingView, as you can see, they are quite close). They don't have to be identical, but should be within pennies if no break in trading occurred between the candles (obviously, this is for intraday and doesn't apply between one day and the next).

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If you need that level of granularity for your trades then you should believe the tape, which is a record of all individual trades that occurred.

A candlestick is just a data point that contains 4 orders within a time period.

It is clear to me that they both recorded the same sequence of data and one just closed out their closing tick on different trade. When close is less than open, it will show the color for that. No big deal.

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  • Looking at all trades is overkill (except as a means of debugging faulty charts); there is no reason an accurate chart shouldn't be straightforward on a 30-minute timeframe. There might be reasonable discrepancies on which tick ends a candle by a few seconds, but since shorter times have smaller price moves, it should be rare for this to noticeably affect the shape of a 30-minute candle. So the kind of difference seen here suggests a deeper problem and is a "big deal".
    – nanoman
    Sep 26 '20 at 5:11
  • Nano, the "close" {which is a silly concept on a 30 minute period} on a 30 minute period is, literally, "the last trade". So yes candles look drastically different if one chart or the other chooses a different "last trade of the 30 minutes". (I guess you're point is, if the stock is fairly heavily traded, that "last trade" (which ever one is chosen) won't change in price much within say a few seconds.)
    – Fattie
    Sep 26 '20 at 15:07
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Compare the raw numbers to see where the discrepancy lies. For example, are they using exactly the same time period for their calculation?. Do their 30 minute candles begin and end at exactly the same time and contain exactly the same price points?

If you have access to Time & Sales, cut and paste the actual trades and determine the O/H/L/C for the time period. Then compare that with the two sources and see which, if any, candle calculation is correct.

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  • Bob, you probably have little/no interest in stuff like candlesticks. They only apply to "full day" trading . (They are "about" the open and close.) It's bizarre/hilarious that some web graphics allow you to pick a "30 minute!" candlestick.
    – Fattie
    Sep 25 '20 at 20:46
  • @Fattie - I did my stint with technical analysis 30 years ago and I have moved on to more practical ways to trade. So yes, you are correct, I have no interest in candles. Sep 25 '20 at 21:28

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