In addition to the regular trading sessions, US stocks also have extended pre-market and post-market trading sessions. Due to the 1-hour spread between daylight saving time and standard time in the United States, the trading sessions in the GMT+8 are adjusted by 1 hour correspondingly. Daylight saving time begins on the second Sunday in March each year, and standard time begins on the first Sunday in November.
(Regular trading session)
|EST||4:00 - 9:30||9:30 - 16:00||16:00 - 20:00|
(EST: daylight saving time)
|16:00 - 21:30||21:30 - 04:00(+1)||04:00 - 08:00|
(EST: standard time)
|17:00 - 22:30||22:30 - 05:00(+1)||05:00 - 09:00|
The US stock exchanges do not have a unified official price for the pre-market and post-market prices. However, brokerage firms adopt the last done price to update the pre&post-market High/Low/Last sale according to the rules.
While the exchanges do not provide official prices for extended trading sessions, official guidelines are available. We offer pre&post-market prices to US stocks based on the guidelines from official Nasdaq and NYSE documents.
One of the most important rules is: odd lot transactions DO NOT UPDATE High/Low/Last Sale.
The following is a screenshot from the exchange:
Therefore, it is possible that the last done price is inconsistent with the pre-market and post-market prices, which is normal.
In addition, different brokers may apply this rule differently, resulting in different pre-market and post-market prices displayed on different platforms. We can check the specific transaction details page to determine the price of the last "non-odd lot transaction".