The term "after-hours" has become antiquated in trading. Pretty much every electronic exchange operates ~23 hours/day (1 or 2 few close periods for maintenance/

The term "after-hours" has become antiquated in trading. Pretty much every electronic exchange operates ~23 hours/day (1 or 2 few close periods for maintenance/book-keeping stuff). Now you'd just refer to those time periods as "Asian hours" and "European hours." Also, remember there is not 1 stock market. There are somewhere around 50-60 exchanges where a company's stock may be traded (counting dark pools), and each of those may have different rules/open periods/etc.