https://docs.magento.com/m2/ce/user_guide/stores/locale-options.html

Locale Options

The locale determines the language, country, tax rate, and other settings that are used throughout the store. The Locale Options determine the time zone and language used for each store, and identify the days of the work week in your area.


Locale Options

To set the store locale:

1. On the Admin sidebar, tap Stores. Then under Settings, choose Configuration.
2. In the panel on the left under General, choose General.
3. Expand  the Locale Options section.
4. Select your Timezone from the list. Then, do the following:
a. Set Locale to the store language.
b. Set Weight Unit to the unit of measurement that is typically used for shipments from your locale.
c. Set First Day of the Week to the day that is considered to be the first day of the week in your area.
d. In the Weekend Days list, select the days which fall on a weekend in your area. (To select multiple options, hold down the Ctrl (PC) or Command (Mac) key.)
5. When complete, tap  Save Config .