This day is traditionally celebrated around the world as May Day, International Workers' Day. A number of cities will have a May Day March.
On the first Tuesday of every month (except January) the board of the Reserve Bank of Australia holds a monthly meeting. At this meeting they decide on (among other things) the current settings for official interest rates. The official interest rates have a significant effect on financial markets, home buyers, mortgage holders and self-funded retirees. The rates are usually announced by mid afternoon.