Replace G'day with welcome.

Hi, I would like to change the text G'Day that appears in the top right hand corner of the admin bar when using the English - Australian language. I have used code in my functions.php file in the past to change Howdy to Welcome but I wasn't using the English Australian version at that time.

If someone could someone please let me know how I can change this text it would very much appreciated.
Thank You
ps. I couldn't read the The Good Support Ticket tutorial as when I clicked the link I got this error message "We are currently over capacity, but will be back any second now.
Please refresh this page, try a different page, or come back in a few minutes.
Many thanks for your patience, see you soon."