Australia here. Do you mean what the legal opening hours are? Because pubs themselves vary, each business owner decides when they want their business to be open. There are some restrictions in specific locations where bars/pubs/clubs must close by a certain time or can't accept new patrons after a certain time (e.g. "2am"), this is due to issues with alcohol-fuelled violence etc where the police are trying to control it somewhat. There are also some places where the liquor license for that specific venue has restrictions as to when they can serve or be open, for example if it were a pub in a quiet residential suburb the license might be subject to restrictions to prevent excessive noise and partying late at night.
The rules in general are fairly liberal. Can buy alcohol any day of the week assuming somewhere is open. It's Sunday afternoon and DH and I popped to the liquor store earlier for some beer, and on the way passed two busy pubs (nothing like a pub lunch on a hot sunny Sunday!) Many big liquor stores in my area will close earlier on Sundays (5pmish), but are open until 10pm/11pm etc on Thur-Fri-Sat as those are the busy nights for people to stock up. There are usually always smaller liquor stores attached to pubs that are open very late every night, but are more expensive.
To me the rules here seem restrictive, because I'm originally from New Zealand where wine and beer is sold in supermarkets. I liked that because I could buy along with groceries so it was less of a fuss. I always buy a bottle of wine at the supermarket when I'm back home visiting, just for the novelty factor!