In the US, stores tend to be open pretty late. It is common to find stores that will be open past 10 pm, and many are also 24/7. However, in many other countries, especially in Europe, stores close at a relatively early hour. You can't just pop out to the store to run some errands at 9 pm under normal circumstances. You have to plan your day to get it done earlier.
Some stores will close as early as 6 pm in many countries in the world. If you need to grab a few items before the evening, be sure to plan in advance.