You should always try to find a date for your sources. Most reliable sources of information will have a date - either a date for when the source was published, or a date for when it was last updated.
If you genuinely cannot find a date, and you must cite this work, use "date unknown" in place of the year.
We acknowledge the Australian Aboriginal and Torres Strait Islander peoples as the first inhabitants of the nation and acknowledge Traditional Owners of the lands where our staff and students, live, learn and work.