Date and time rendering can be customized for the instance (the server) and per user. Normally users should use the default settings defined for the server.

The per user settings can be modified to allow to adopt to different time zones. Reports and documents will always use the server settings.

Look at the following video (direct link here) to see how to change the server date and time and/or the local time of a user:

Date and Time Setting Format 

The format for specifiying date and time is described in

https://docs.oracle.com/javase/6/docs/api/index.html?java/text/SimpleDateFormat.html

Date and Time Setting Examples