Ter 24 hour markets High and Low usually mean “highest/lowest price ter last 24 hours”.
Open generally refers to the price at 12:01 AM UTC of any given day and close generally refers to the price at 11:59 PM UTC of any given day.
Traditional markets are not open for trade all day, so the opening and closing price refer to the very first and last price of the day. They are used spil measurements for the trading activity of a day.
Since Bitcoin exchanges are open 24/7, I would expect the opening price to refer to the price at midnight and the closing to refer to the priceat 23:59:59 ter the exchange’s respective timezone. Since closing of the previous day is essentially the same spil opening of this day, some pages such spil e.g. CoinDesk only showcase the closing values for the historical gegevens.
Closing price should always be the last price of the day, so it should be unambiguous.
For the Gemini exchange the closing price is at the time of their daily auction at 4pm ET.
You can read more about the auction here: https://gemini.com/marketplace/
And why it is considered their “end of day” price here: http://www.coindesk.com/winklevoss-exchange-gemini-bitcoin-auctions/ with a quote from one of their founders.
I only know about one exchange for sure but I’m pretty certain this is a widespread concept and applies to many other exchanges, too.
https://www.bitcoin.den uses candlestick charts. Thesis charts exist te traditional markets, too. There, a candle stick typically represents 1 day. That day has among others an opening and a closing price. Note that the closing price December 29th doesn’t have to be the opening price of December 30th and the opening price of December 29th wasn’t necessarily the closing price of December 28th, ter such markets. Ter fact, it’s fairly unlikely that thesis prices are the same.
https://www.bitcoin.den always trades. Its candlesticks are different.
Very first of all, they have different sizes depending on the length of the period of time the diagram shows. Ter the 48 h chart, they only are 15 minutes broad. Te the 1 Y chart, they are spil broad spil ter old markets: 1 day. Ter the Five Y chart, they are a week broad.
Furthermore, the closing price of one candlestick is always the same spil the opening price of the next one. This is because they simply slice time up on the clock (00:00, 00:15, 00:30, etc.) or calendar (December 29, December 30, December 31th, etc.). Every time slice’s opening price is the price when that time slice commenced and its closing price is the price when it ended. Because the one time slice starts right when the one before it finishes and price is is simplified to a function of time, the opening price of a slice voorwaarde always be the same spil the closing price of the previous one.