Mercury's location in your birth chart influences all of this! Mercury never travels more than 28 degrees from the Sun, so many people will have Mercury in the same zodiac sign as their Sun.
From Monday to Friday, the stock market remains open from 9:30 am to 4:00 pm, EST. PST time is 6:30 am to 1:00 pm.
Market half-day holidays may include July 3 or 5, the day after Thanksgiving and/or Christmas Eve, depending on how the calendar falls in a given year. In that case, Nasdaq will close at 1:00 pm Eastern Standard Time. You can see the Nasdaq holiday calendar here. There are also pre-market and after hours trading sessions available, also known as Extended Markets. For Nasdaq, pre-market trading hours are 4:00 am to 9:30 am, Eastern Standard Time. After hours runs from 4:00 pm to 8:00 pm, Eastern Standard Time. Certain brokers have different pre-market and after hours trading times (for example, TD Ameritrade limits pre-market trading between 8:00 am and 9:15 am).