Default date, time, and language settings for the whole organization
The administrator can set up the default date, time, and language for the whole company in Configuration → Account settings:
The administrator can change the date, time, and language settings for an employee
If you (as an Administrator) want to change the date and time format or language for one employee:
Open Configuration → People.
Double-click on the particular employee
Click the ellipsis [ ...] symbol.
Select Profile settings, make the changes and click Save.