When did the separate colonies unite into a federation of states called the Commonwealth of Australia?

• {ts '1901-01-01 00:00:00'}
  Explanation:

  "The separate colonies united into a federation of states called the Commonwealth of Australia on 1 January 1901."
• 1 January 1801
• {ts '2000-01-01 00:00:00'}
• {ts '1950-01-01 00:00:00'}