Complex sentence: In 1948 the New Zealand Parliament passed the "British Nationality and New Zealand Citizenship Act 1948", and from 1 January 1949 all New Zealanders became New Zealand citizens.
Split into simpler sentences: In 1948 the New Zealand Parliament passed the British Nationality and New Zealand Citizenship Act 1948, altering the New Zealand nationality law. From 1 January 1949 all New Zealanders became New Zealand citizens.