Time Not Changing On Formula Field


I have a formula field as follows:

DATETIME_FORMAT(SET_TIMEZONE(NOW(), ‘Australia/Sydney’), ‘HH:mm’)

However, the field seems to remain static - the time never actually changes :-/

Can anyone spot an error in the formula, or is there a better way to do it?

The goal is just to show the current time in a given timezone. Just the time, not the date.